18. Weed Control (part two)

Weeds are always seeking to invade the healthy soil of a garden.  They can easily become intimidating and overwhelming, and it may seem like you can never win.  But it’s not true! – there are many good options for weed control, and I’ve already written about the design factors and mechanical controls for weeds.  Now let’s take a look at herbicides:

Part of my motivation in writing this is to answer a very common question: how bad are those weed killers and should I use them?  As with a lot of things, the short answer is “it depends” – on the specifics of your garden situation and the specific herbicide in question.  Herbicides can be generally defined as substances toxic to plants, typically coming in spray or granular form.  They are divided into 2 categories according to when they are effective:  pre-emergent and post-emergent, and there are natural and chemical versions of each.

Pre-emergent Herbicides
Pre-emergent herbicides are applied before weeds emerge from the ground, preventing seeds from sprouting or killing seedlings as they sprout.  They effect all seeds in the ground that are trying to sprout, and the chemical ones typically last for 6 to 8 weeks.  The advantage is that they don’t effect plants that are already there. If you’re planting a meadow of pre-grown native grasses, you can use a granular chemical pre-emergent to block the sprouting of weeds that will compete with the grasses.  Pre-emergents are also commonly applied for weed control in lawns.

The key is in the timing of the application, which must occur one or two weeks before a certain weed is going to sprout.  This limits their effectiveness and also increases the chances for environmental damage.  If applied at the wrong time you are simply putting chemicals in the ground with no positive effect and many negative ones.  This is especially true of lawn ‘weed and feed’ products – sounds like an efficient combination, but you don’t need to apply fertilizers and herbicides at the same times or frequencies, so you are most likely applying excessive chemicals which then move into the larger environmental systems, especially contaminating our water – creeks, rivers, and the bay.

The chemicals used in pre-emergents are said to have similar hazards as those used in post-emergents, which I talk more about below.  The main natural alternative is Corn Gluten, a byproduct of corn processing.  This is spread as a powder or granule and then wet down to cover the ground.  The one direct experience I have with this product was pretty good for weed control, but we were surprised by the smell of it when applied, a sort of compost-y garbage-y smell, so be sure to test it out on a small area first.  The timing issues with pre-emergent herbicides make these less popular than the post-emergent ones.

Post-Emergent Herbicides
Post-emergent herbicides are ususally sprayed directly on the weed you want to get rid of.  Most of them are indiscriminate, meaning that any plant they come into contact with will feel the effects, so you have to be careful in a garden with established plants.

The more environmentally safe post-emergent herbicides are typically called “contact” herbicides.  This is because they will kill any plant parts that they come into contact with, but leave other parts alone.  Common contact herbicides have active ingredients such as Vinegar (acetic acid), Clove Oil, Citrus Oil, or a type of soap, referred to as Herbicidal Soap.  These are all relatively benign ingredients that won’t linger and harm people or animals. They do, however, leave the underground parts of the plant there, so many weeds will tend to grow back.  This obviously makes the job harder, and some argue that contact herbicides are a waste of money and hand pulling or sheet mulching is far more effective.  Others argue that because of this drawback, the only solution is to use a chemical herbicide.

Chemical herbicides enter the plant’s systems and kill the entire plant by disrupting biochemical processes.  The most common retail weed killers of this type rely on glyphosate, a chemical introduced by Monsanto Corporation in the 70’s as Roundup.  Chemical herbicides can be seen in many ways as the “nuclear” option – very effective, but with many lasting and toxic side effects. I must confess that I have turned to these types of herbicides in certain situations, but in researching for this piece I have become convinced that there is a very real potential for environmental damage.  I still think they can have a limited place, but a truly sustainable garden would never use them.  If used, they must be carefully and judiciously applied, following all the directions precisely.  Especially important is avoiding their use in vegetable gardens, or areas where you can’t keep children, pregnant women, and pets out of for 24 hours after application.

The reason for concern is that these are chemicals that are designed to cross into the internal systems of a plant and disrupt them.  Many believe that they can disrupt similar processes in humans and animals, and some of the research backs this up.  The chemical companies claim that they are safe when properly used, but many others believe that any exposure is unsafe.  There is a call for more testing, but generally the implications of the research so far are quite bad: possible contributions to human birth defects, cancer and other reproductive problems, and damaging to kidneys and the liver.  They can also be harmful to soil organisms, which can weaken the environment for all plants, leading to increased plant disease and decreased nutrient uptake in plants.  Issues such as the validity of various research, level of exposure that is toxic, etc, gets quickly tied up in global corporate politics too complicated to get into here (see the references below).

Overall, Mechanical Methods are Better
Based on what I’ve read, and my personal experience, I would have to say that any herbicide is of limited use in the home garden.  The chemical ones are just too environmentally damaging to use except in extreme cases in very controlled conditions, and the natural ones are not usually as effective as mechanical means.  I encourage you to go out there and try things yourself to see what works for you, just be sure to read the label and be very careful with those chemicals.  Happy weeding!

Golden Gate Gardening, by Pam Pierce

Bay Friendly Gardening Guide, published by the Alameda County Waste Management Authority, www.stopwaste.org

The New Sunset Western Garden Book, published by Sunset

Peaceful Valley Garden Supply, www.groworganic.com

What Biotech Pesticides Are Doing to Our Bodies, by Leah Zerbe, Rodale News, www.rodale.com  September 12, 2011

Roundup: Birth Defects Caused By World’s Top-Selling Weedkiller, Scientists Say, by Lucia Graves, Huffington Post, www.huffingtonpost.com  August 24, 2011

Weed Killer Kills Human Cells. Study Intensifies Debate Over ‘Inert’ Ingredients, by Crystal Gammon, Environmental Health News, www.environmentalhealthnews.org  June 22, 2009

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17. Weed Control (part one)

Yikes, those weeds are out of control, what should I do?  I don’t want to use chemicals, but hand pulling is back breaking!  Are there some alternative, organic weed killers or other techniques out there that are environmentally friendly?  Yes, you have a lot of options and I’m sure there is something that will work for you…

First, to be clear: weeds are not some botanically specific category of plants, rather they are the unwanted ‘pest’ plants in your garden.  Typically they spread easily, and often invasively crowd out more desirable plants.  On one hand, a native plant could be a weed – for example Poison Oak is a California native plant, but I certainly don’t want it in my yard.  Conversely, the Dandelion is usually called a weed, but it can be used in salads, so it may have a place in the garden.

Why Fight the Weeds?
Why not let that pretty yellow flowering plant grow in your yard?  The very common weed form of Oxalis may look nice in the early spring, but it is a bad idea to let weeds like this thrive.  They are competing for and consuming the things that other plants need:  sunlight, soil nutrients, and water.  The longer you let weeds grow, the more widespread they become, not only the visible plant parts, but also the root system and underground bulbs.  Some weeds can re-sprout from any little part of the plant left in the soil.

Many weed species can flower and develop seeds in just a few weeks, and some can produce thousands of seeds from a single plant.  It is said that urban soils typically contain 6 or 7 year’s worth of weed seed, with more coming in on the breeze, and from birds and other critters, so this is a battle that will not be won overnight.  But fear not, it isn’t hopeless, you can stave off the invaders!  Your possible weed control techniques can be divided into a few categories:  Design Factors, Mechanical Methods and Herbicides.

Design Factors
There are several ways a good planting design helps to reduce weed growth.   First of all, don’t plan on leaving any bare areas in your garden.  By including some evergreen groundcovers in the planting design, such as Beach Strawberry (Fragaria chiloensis) or Yankee Point Ceanothus (Ceanothus griseus horizontalis ‘Yankee Point’), you can fill in the space between your larger shrubs and block sunlight from reaching the ground.  The way in which you water your garden also has an impact.  Use drip irrigation with emitters that only apply water to the root zones of the plants you want to grow, and you limit the water available water for the weeds.  Lastly, the design should require the installation of a thick bark mulch layer in all planting beds.  This will reduce your weed problems by keeping sunlight from the soil surface where the weed seeds are trying to germinate.  Mulch also forces the weed to root in this loose material so that it is easier to pull.

Mechanical Weed Control
1.   Pulling  Weeds
Mechanical controls are techniques that involve tools and/or manual labor. Pulling weeds up by hand is the most common method.  It is most easily done when the soil is somewhat moist (but not saturated) and before the plant has gotten too big.   There are different weeds coming up at different times of year, so you have to keep an eye out for their growth patterns.  It is also very important to pull the weed before it has time to produce seeds.

Sometimes watering an area in advance is a good idea to allow for better weed removal.  You can take this further by “pre-sprouting” a planting bed, watering it thoroughly before planting and letting the weeds come up, then pulling them.   Other techniques commonly mentioned are hoeing and rototilling instead of hand pulling for large areas, but in most garden situations I think that stirring up the soil too much does more harm by bringing weed seeds deeper in the soil to the surface.

2.   Mowing
If you have a larger area and no time to hand pull, then at least cut the weeds down to the ground before they go to seed – many “lawns” are really just grassy weeds kept mown down.  This will keep things under control to some extent, but it is not going to eliminate all the weeds.   You will have to time things very well to prevent any of the weedy grasses from going to seed, but certainly there will be less seed added to the soil overall.  Mowing is also important in large areas near wild lands to reduce fire danger.

3.   Sheet Mulching
For big areas where you are starting from scratch, sheet mulching is one of the best options.  Basically you are laying down layers of compostable materials to smother all the plants in a given area and improve soil quality.  I’ve already talked about the details of sheet mulching, so refer to that for more information.

4.   Soil Solarization
An interesting option in areas with consistent sun is this technique where you put down a layer of clear plastic, seal the edges, and let the sun heat up the soil to kill weed seeds and other bad fungi and pests.  Read up on the details of this technique before doing it – you need a lot of sun, and you can’t leave it too long or it will start harming the beneficial living things deeper in the soil.  It also only kills off weed seed in the very top layer of soil, so be careful not to bring deeper soil to the surface, or you will have weeds anyway.

There is a lot of complexity to the options for herbicides – substances applied to the soil or the weed to eliminate it.  See Part Two for more on this subject.

Overall Strategies in the War on Weeds
If it all still seems overwhelming, consider the divide and conquer method, which I did when I started my garden.  Be realistic about your time and resources, and apply different methods to different parts of your yard accordingly.  I almost completely ignored the back edge of my property for the first few years, just doing a quick hand pulling of the weeds and mulching once a year, not obsessing about getting all the roots, just keeping things from going to seed.  In front of that I laid down a 6 foot wide strip of plastic topped by bark mulch to create a sort of “battle line”.  Then I simply mowed the center part of my yard for a few years to keep things from getting too out of control, eventually applying cardboard sheet mulch.  That left me with relatively smaller side beds and areas closer to the house for hand pulling of weeds.

After 5 years, I can definitely say that there are less weeds for me to worry about, so do what you can, and don’t despair!

Golden Gate Gardening, by Pam Pierce

Bay Friendly Gardening Guide, published by the Alameda County Waste Management Authority, www.stopwaste.org

Gaia’s Garden – A Guide to Home Scale Permaculture, by Toby Hemenway

The New Sunset Western Garden Book, published by Sunset, www.sunset.com

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16. The Native Meadow Experiment – Installation

It has been over a year in the making, but I’ve finally gotten to a satisfying stage of this experiment – the installation.  (see this earlier posting to read about the first few steps.)  Due to the very rainy fall we had around here, the soil has been too wet to work with for several months, but we’ve finally had some dry weather that allowed me to get the soil prepared and the plants in the ground.

Soil Preparation
I’ve already discussed the importance of healthy soil and the soil testing I did to determine how to prepare the soil for my native meadow.  This started with sheet mulching that I applied almost a year ago, hopefully getting rid of a lot of the weeds, and adding a bit of organic matter.  Now its time to improve the health and chemistry of the soil by loosening it and mixing in amendments.  I put down a pretty thin layer of cardboard, which is almost entirely decomposed at this point, so I just needed to rake up the mulch layer and store it on the side so that I can amend the soil.

The soil has a fair amount of clay and is definitely compacted, so the first step is to stir it up and break up the chunks to get a finer texture that can easily have the amendments mixed in.  The specific recommendation of my soil testing report is to loosen to a 10” depth.  This is some hard work, but I can see right away how the soil texture is improved for plant root growth.

Once the soil is all loosened up, I’m ready to mix in the amendments.  There are many types of amendments that vary depending on the soil you have.  In my case the soil testing report gives some specific recommendations “3 cubic yards of nitrogen stabilized organic amendment and 110 pounds of Calcium Carbonate Lime per 1,000 square feet of area.”  Most Bay Area soils are going to benefit from additional organic matter which helps counteract the dense clay and adds nutrients.  This material, which is usually ground up tree bark or coarse sawdust, needs to be nitrogen stabilized to avoid the leaching of nitrogen from the soil (it can actually suck up nitrogen from the soil if it isn’t).   The lime is an amendment specific to my soil, which has a very low pH, added lime will raise the pH to the middle range that plants prefer.  I’m also mixing in a packaged all-purpose fertilizer that contains of a whole host of beneficial organisms and nutrients.  Mainly I wanted to be sure to get some mycorrhizae in the soil and this mix has 3 kinds of endomycorrhizae, and 5 kinds of ectomycorrhizae, which is great.  Without getting too deep into a very large subject, mycorrhizae are a type of fungi that live on plant roots and form a beneficial symbiotic relationship, helping roots uptake nutrients and water and getting food in exchange.  There are a lot of other benefits as well – these fungi are a basic part of healthy soil that are often lost in urban areas.

One important thing to understand about soil amendment is that the loosening and adding of amendments does increase the volume of soil you have (sometimes called fluffing), so expect for the planting area to get a little higher.  Once you have mixed in all the amendments thoroughly to a 6” depth you lightly compact the soil with a barrel roller or simply by walking on it to even things out.


Plant Installation
Now that my soil is ready its time to put some plants in the ground.  See my earlier posting about the plant choices I made, now it is simply a matter of laying them out in the patterns I want, spaced according to mature size, and planting them.  I have chosen plants that are small to start with, both because of cost and because they are typically younger and more vigorous, better able to adapt to a new environment.  They do need to be treated pretty gently during planting and kept watered because they start with such a small root mass.

Once the plants are in, a thick bark mulch layer should be added, typically 3” deep, but tapering thinner at the plant base since you don’t want to block new leaves and branches sprouting up from the edges of the base of the plant.  Mulch is of course critical in your garden for many reasons, such as preserving soil moisture, preventing erosion, adding organic matter to the soil, and blocking weed growth.  I also re-installed the expression of the Golden Ratio spiral in my landscape design, using stepping stones for most of it and river rock for the smaller section.  It is very satisfying to have these steps complete, now I just need to keep up the watering and watch the grasses grow!

Designing California Native Gardens, by Glenn Keator and Alrie Middlebrook

Handouts and Notes from my attendance at the California Native Grass Association’s workshop:  Using California Native Grasses in the Water-Conserving Landscape      www.cnga.org

Creating a California Native Meadow by David Amme, as published in Grasslands, A publication of the California Native Grass Association.

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15. Landscape Sustainability – Wastewater Reuse

There are many things having to do with water in the landscape that can be better designed for sustainability, such as rainwater harvesting and stormwater.  Any garden needs water to thrive, especially if you are growing your own food, but drinkable water is a precious resource that is best saved for quenching your own thirst.  We use a lot of water in our homes for washing and cleaning that really doesn’t get that dirty, so why not use it to water the yard?

Wastewater on My Plants?
Yes, it is possible to use 15-40% less drinking water by diverting some of the dirty water that normally goes down the drain.  Household wastewater is divided into two types: grey and black water.  Greywater is generally defined as any wastewater except what is flushed down your toilet.  The official definition given by State of California is a little different, including only waste water from laundry washing machines, bathroom sinks and showers/bathtubs.  The State doesn’t like to include kitchen sinks or dishwashers because of the potential hazards to human health from bacteria and other organisms.  However, the water from your washing machine or shower is relatively clean and has potential for reuse.  Inside the home, greywater can be reused for flushing toilets, but I want to focus on landscape uses, namely irrigation.

Government Regulation
Greywater systems have been used for a long time in more rustic settings, and pioneered by Californians for modern dwellings since the 1970’s, with little government oversight.  My favorite is the ‘garden shower’ where you surround an outdoor shower with dense, water loving plants and the drain connects directly to a distribution system to water them – but you obviously need a lot of land area and privacy to do that!  In 2009 the State of California revised their laws regulating the uses of greywater to allow certain types of installations.  The legal details are too long to list here, and are still being tinkered with by our lawmakers.  But generally a greywater system that only uses water from the washing machine is very lightly regulated, and a system using bathroom sink, shower or bathtub water is allowable with the proper permits.

Laundry to Landscape System
This leads us to the simplest and cheapest option for home greywater use, the laundry to landscape system.  This involves a diversion of the water from your laundry’s waste pipe to a low-tech distribution system using mulch basins.  It generally does not require a permit, but varies by City and County, so you should confirm it before starting.

A washing machine can generate an average of 15 gallons of water per day, per person, and you can route all of that into the landscape – no small amount!  If you’re already on track with a sustainable landscape of native and drought tolerant plants, you can still route this greywater to a special area of higher water use plants, especially fruit trees or non-tuberous vegetables.  Greywater should not come into contact with anything you directly touch or eat, so don’t use it to irrigate tuberous root crops like potatoes, carrots, rutabagas, etc.

1.   Diverting the Water
The first part of the system is a bit of plumbing to divert the water from going into your sewer lines.  This involves a T connection with a valve so that you can direct the water outside when you want, and a vacuum breaker.  Details on all of the pieces needed can be found in the resources listed below, but generally it is a relatively simple do-it-yourself project.  The reason for the valve is so that you always have the option of putting that water into the sewer pipe.  This could be necessary if you happened to need to use chlorine bleach on a certain load, or if the soil is already extremely saturated and the greywater will be forced to run across the surface (not legally allowed).

2.  Dissipate the water into the landscape
The second part of the system is piping and mulch basins to distribute the water into the soil.  In this low-tech system we are avoiding a connection to a typical drip irrigation system so that we don’t have to worry about micro-filtration to prevent clogs in the tiny holes of drip emitters.

The interesting part to me is the mulch basins.  The greywater should not come into direct contact with people or animals, so the idea is to have the outlet of the piping below ground in a mulch filled depression that allows temporary pooling up and rapid soaking into the soil.  The best low-tech detail I’ve seen is to cut off the bottom of a black nursery pot and use it as a ‘shield’ for the outlet pipe.  You want to keep the outlet pipe about 4” above the mulch, but below the ground level, so the pot creates a chamber for this.  This is critical because it prevents the pipe from getting clogged up; if all of your outlet pipes became clogged the water won’t have anywhere to go and you’ll break the washing machine.  Layout, size and number of mulch basins is determined by some calculations on the amount of water you will have and what area it will serve, described in the resources listed below.  There are many other technical details that I’m not able to describe in this short piece, so be sure to read up on it or hire a professional to help you with the design and installation.

New Water Use Habits
Once you have a laundry to landscape system installed, there are a few easy changes to make to your water use habits.  The main one is using cleaners that are safe for the garden, avoiding things like chlorine, boron/borax, and high salt content.  In the Bay Area we are fortunate to have retail stores that sell laundry detergents specifically for greywater going to irrigation systems, they can also be mail ordered.  You might also consider changing your laundry schedule, spreading it throughout the week so that the plants are watered on a regular basis.  You should also keep up with periodic maintenance of the system, monitoring for clogs, and replacing the mulch in the basins annually.

Hopefully you will find that the knowledge of where this water is going makes you more conscious of your water use in general.  As with rainwater harvesting, a greywater system is a practical sustainability feature that also mentally connects you to the ecological systems that you are a part of, an important larger goal of sustainable design.

I’ve really only put a few ripples in the surface of this topic, there are tons of different systems and lots of groups providing free information on them, check out these references for all the details:
San Francisco Greywater Manual for Outdoor Irrigation,  sponsored by the SFPUC, downloadable at http://sfwater.org/index.aspx?page=100

Create and Oasis with Greywater, Oasis Design, www.oasisdesign.net

Greywater Action, www.greywateraction.org and for greywater friendly products specifically: http://greywateraction.org/content/greywater-friendly-products

Water Management, Occidental Arts and Ecology Center workshop led by Brock Dolman, fall 2012

Legal Greywater Design for Small Scale Applications in California, published by The Water Institute at OAEC, www.oaecwater.org

State of California Greywater Code, downloadable here http://www.hcd.ca.gov/codes/shl/2007CPC_Graywater_Complete_2-2-10.pdf

Clean Water Components, a supplier of equipment for all kinds of sustainable water projects http://www.cleanwatercomponents.com/

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14. Patterns in Nature (part three)

Time to talk again about patterns in nature and the connections to landscape design.  In earlier posts I wrote about the Golden Ratio, and branching patterns.  I’d like to get into good ‘ole geometry this time, so let’s start back in something like 6th grade and think about circles, squares and triangles and see where that takes us…

Simple Geometric Building Blocks
Way back at the beginnings of modern science, people like Pythagoras saw basic geometric forms as the building blocks of everything in nature.  He found circles, squares, triangles, pentagons and hexagons in all kinds of natural forms and saw their recurrence as evidence of inherent harmony and regularity.   Although it can be tough to find them in their literal, symmetrical forms, these shapes do seem to underlie all kinds of natural phenomenon.  For example, there are hexagonal forms in things as varied as bee hives, snowflakes, and rock formations such as the basalt rock columns of Devils Postpile near Mammoth, California.

The 3-D version of the five basic shapes are the Tetrahedron, Cube, Octahedron, Dodecahedron and Icosahedron, together called the Platonic Solids.  These are the only 5 possible Regular Polyhedrons, those that have faces with the same shape and size.  Since those were more mystical times, these shapes were a big part of what is now called Sacred Geometry, a sort of mystical / philosophical idea that these pure forms underlie all the forms in nature and are evidence of a conscious, intentional creator behind it all.  I won’t even attempt to prove or disprove this concept, my point is that these simple shapes have been seen as something of great significance for quite a while.  In fact, the concept of all matter being made up of these shapes isn’t all that far from the modern scientific conception of atoms and molecules.

Both the 2-D shapes and the Platonic Solids were given many symbolic meanings, for example being associated with the 5 elements:  tetrahedron = fire, cube = earth, icosahedron = water, octahedron = air, dodecahedron = the void/ether.  Because of their commonality in nature and their symbolic meanings they are found in human-designed structures throughout history.  If a person is so inclined today, these geometries can again serve as inspiration for giving some symbolic meaning to a design.

The Vesica Piscis
A simple example is that of the vesica piscis, which is the overlapping of two equal circles so that the outer edge of one touches the center of the other.  The shape formed in the middle resembles a sort of lens or eye shape that has been connected to many different abstractions.  For example, it can be seen to resemble the overlapping of the sun and moon in an eclipse, with the middle piece symbolizing a gateway between the opposing worlds.  Connecting the intersection points yields an equilateral triangle, and a hexagon can be drawn by connecting the intersections of the triangle, as you see in the diagrams above.  Before the time of computer drafting, people were able to generate these forms with simple drawing tools and use them as a basis for all kinds of architectural elements. I used is as the basis for a theme camp design as you can see below.

Tile Patterns
You can take this method of connecting intersection points further and further and generate some really interesting patterns that you will recognize in ceramic tile shapes, mosaic patterns, weavings and other pieces of art and architecture from many time periods and cultures.  By simply inscribing circles within squares (called the “squaring of the circle”) and connecting intersection points you can derive all kinds of patterns that can be used in paving designs, such as those shown below.  Religious architecture around the world works off these kinds of basic geometries and the connecting of points, using them as symbolism for their beliefs.  For example the gothic window frame is formed by the edges of 3 circles overlapping in a triangular arrangement to symbolize the 3 aspects of the Trinity.

The Geometric Depths
In some of the books I read, they really start to go deep on this idea and draw connections between certain numbers, shapes, and proportions that start to get a little too mystical for my scientific upbringing.  However, I do find it remarkable how many different cultures and societies have utilized basic geometric shapes to symbolize deep concepts and philosophies.  I definitely see value in bringing some of that into a design as a fun way to put a little more meaning into the shapes, colors, and patterns used.  Some related approaches to design based on patterns thought to be inherent in nature are Feng Shui and Vastu Shastra, but that’s a whole other topic that will have to wait.

At a more practical level, these geometries can form the basis for all kinds of patterns in the landscape, from patio tiles to fencing and trellis structures.  These sorts of patterns may not seem to connect us to nature quite as directly as branchings or Fibonacci proportions, but in a sense they represent the basic properties of the space that nature grows within.

Patterns in Nature, by Peter S. Stevens

Sacred Geometery, by Miranda Lundy

Sacred Geometry – Philosophy and Practice, by Robert Lawlor

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13. The Native Meadow Experiment – Plants

The next step in replacing my backyard lawn with a native meadow is to create a precise planting design and plan the installation.  (See this earlier posting to read about the first few steps of this experiment.)

My goal is to re-create a grassy meadow resembling what would have been in this area prior to human impacts.  In terms of plant communities, it is likely that where I live along the eastern edge of the San Francisco Bay was a Coastal Prairie plant community.  The plants of the Coastal Prairie are primarily grasses, some small shrubs and numerous wildflowers.  It amounts to a pretty long list of fun choices, including things like Purple Needle Grass, Sky Lupine, Pacific Coast Iris, and California Poppies.

Plant Selection and Layout
Narrowing down the choices involves considering the site specific environment as well as personal aesthetic preferences.  Since the starting point is a list of plants native to this area, many things are already working for us – for example all of the plants are used to the local weather patterns and shouldn’t need a lot of extra water once established.  The basic site factors are: exposure (full sun to part shade in my case), soil type (amended clay), water use (drought tolerant).  Disease and pest resistance is also important – native plants naturally resist the native pests, but there are plenty of non-native ones out there, and some plants are more susceptible than others.  Other important site factors that may come into play elsewhere are deer resistance and fire resistance, but they’re not a concern in my small fenced backyard.

Aesthetically, you want to consider the mature size of the plants, what time of year they flower, and when they are dormant.  The arrangement should try to provide enough variety so that something is looking good year round; other than that things can vary quite a bit according to personal preference.  Since this is an experiment for me to study native plants, I’ve decided not to go with a straight “restoration” approach where the design resembles a rectangle of wild prairie cut out of nature.  I want to have more variety so I can watch and learn about how the different plants grow.

Also, I can’t resist expressing my interest in geometric patterns in the layout of the plants. I’ve already got a Golden Section rectangle as a frame, and am going to express the inscribed spiral as a stone pathway.  To work within that, I’ve decided to plant the grasses in widely spaced rows, leaving space for the other shrubs and wildflowers to fill in.

Even though we are using native plants that don’t usually require irrigation after they are established, you will still need to water them for the first 12 to 18 months.  It is also possible that during big heat waves or extended dry periods some plants will need extra water to stay healthy.  Depending on the size of the area and your available time and money, the options vary from hand watering to a fully automatic drip irrigation system.  In the case of my small backyard, hand watering will be easy to do, so I won’t install an automatic system.  However, I did consider where I would place a sprinkler and hose to be sure not to block the good spots.

Planning the Planting
The plants I’m using can be divided into three rough categories: grasses, year round shrubs, and seasonal perennials/annuals.  The focus here is the grasses because they will be planted first.  This is for two reasons:  they are cool season grasses which start their growth spurt in the early winter, and they also need to get a head start to become well established before there is too much competition.

Remember that one of the biggest challenges in establishing a native grass and wildflower meadow is weeds.  In addition to the sheet mulching, you want to time the planting to maximize conditions for establishment.  For a plant to get established, it needs time to adapt to its new environment, grow its roots into the new soil and ramp up its growth processes.  During this time they need extra water and regular removal of weeds that will compete for sunlight, water and nutrients.  If the plant is put in the ground at the beginning of its primary growth period it can usually become established in 12 to 18 months.  So getting the grasses in early allows them to get going before the spring weeds come up and get as much growth time as possible before late summer dormancy.

Another big decision is whether to use seed or pre-grown plants.  In my case, because it is a small area and there is definitely a lot of weed seed in the ground, I’m using nursery grown plants from containers.  This can get expensive in larger areas, but the battle with the weeds will be harder if you use seed.

In the late spring, I may add in some other shrubs and ground covers  but any annual wildflowers should wait until after the grasses are established – at least one year.  As you can guess, an annual plant that completes its life cycle in one season is going to grow faster and larger than a plant that has a multi-year life cycle.  Therefore the other plants need to be well on their way before you introduce the fast growing wildflowers.

Finding the Plants
Your plant selection is also dependent on what plants can be found at local nurseries in enough quantity to fill up the space.  When dealing with native plants, and especially seasonally dormant grasses, this can be a bigger issue than you might think.  People tend to buy plants that look healthy and are flowering, so a nursery isn’t going to keep a large inventory of a plant when it is dormant.  Native plants can also be harder to find than non-natives at the typical nursery.  See my links page for more information on native plant nurseries.

When to Plant
Generally you want to plant any natives in the late fall, the exact timing of the planting depends on the amount of rain and the temperatures.  Ideally you get them in the ground after a little bit of rain, but before things are completely saturated, and before the days get extremely short, or particularly cold.  This year we had a lot of early rain and the soil got quite saturated before I could get things ready, so now I’m waiting for a dry spell before getting started.  I’m loving all the rain, but hoping for a week or two of dry weather soon!

Designing California Native Gardens, by Glenn Keator and Alrie Middlebrook

Handouts and Notes from my attendance at the California Native Grass Association’s workshop:  Using California Native Grasses in the Water-Conserving Landscape      www.cnga.org

Creating a California Native Meadow by David Amme, as published in Grasslands, A publication of the California Native Grass Association.

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12. Landscape Sustainability: Rainwater Harvesting

Sustainability in the landscape may seem easy – green is green, right? – but there is a lot more to it than that.  I’ve already talked about what sustainability means to me and there are many specific areas where a landscape can be more sustainable; this time let’s talk about rainwater harvesting.

The sustainable attitude towards the rain falling on your property is to take care of it on site rather than piping it away to cause problems elsewhere.  I’ve already gotten into the different things you can do to manage your stormwater on the ground.  When it comes to rain falling on your roof or other raised paved areas, the best thing you can do is make use of this valuable resource by collecting it and storing for use later.

The focus here is rainwater harvesting for garden use, also referred to as non-potable uses (not for human consumption).  These systems do not typically require complicated engineering, and we are lucky to now have great resources available for basic residential systems.  In California, the challenge is our extremely long dry season, which means that it takes quite a bit of storage capacity to last all summer and fall, and large tanks can get expensive.  But that doesn’t mean its not worth it to have a system that provides you with sustainable and free water during dry spells and into some of the summer months.

Typical System Components:
1. Collection Surface
Your system starts with the collection surface, the roof or other paved area and the point that the water flows to, usually a gutter.  The material of the roof surface and the debris that collect on it are important to keep in mind.  Most homes have roofs with asphalt shingles which add small particles and pollutants to the rain water.  A metal roof is preferable, but any surface can be dealt with, at least for garden use.  If you have trees overhanging your roof, you will end up with fallen leaves, twigs, and other debris that needs to be kept out of your piping.  This means screens on your gutters that are securely attached and well maintained.  You can also install a debris separator just below a cut-off downspout to create a single point for screening.

2. First Flush Device
From the gutters, the rainwater flows to some type of first-flush device.  This diverts a certain amount of the initial rainfall away from your storage tank to reduce pollutants.  Especially after a long period of no rain, the first bit of water that flows across your roof will pick up quite a lot of pollutants and debris, so the idea is to let that water flow to the storm drain or landscape as it would have before you had a collection system, keeping pollutants and pipe-clogging particles out of your storage tank.  The typical residential system uses a pretty ingenious mechanical device that has a floating ball in a vertical pipe that seals the connection once the pipe is full. The exact volume of the first flush should be calculated by an experienced professional specifically for your project, but generally ranges from 1 to 10 gallons per 1,000 s.f. of collection area.

3. Storage Tank
Ultimately, the rainwater reaches a storage tank.  I won’t get into the calculations for sizing a tank, but your basic yield is about 620 gallons per 1” of rain falling on 1000 square feet. One important thing to keep in mind that water is heavy, about 8.35 pounds per gallon. Try to locate your tank so that if a disaster was to occur and it burst or fell over, it wouldn’t be catastrophic to the occupants of the building or other valuable equipment.  If there is any doubt, you should consult with an architect or engineer.  Another potential hazard is growth of bacteria or insects in your tank.  Mosquitoes make quick use of still water to breed, so the tank needs to be sealed against this.  There also needs to be an overflow outlet at the top so that when the tank fills up, the water has somewhere to go, ideally into a bioswale or rain garden.

4. Distribution System
Downstream of the tank you have your distribution system, which is usually no different than a typical irrigation system.  Ideally you are able to collect and store the rainwater uphill of your garden so that you can gravity feed irrigation lines.  If that’s not possible, then you will need to have a powered pump that either pressurizes your lines, or takes the collected water to a storage tank the high point of your yard for gravity feeding.  Of course a pump will add cost and maintenance time, but there are some DC solar pumps made for this type of use that are relatively simple.   If nothing else you can resort to good old manual labor and have a faucet at the bottom of the tank that can be used to fill watering cans.

Rainwater Harvesting for Indoor Use
The simplest rainwater harvesting systems are used to irrigate the garden, but don’t forget the possibility of bringing it back into your house for flushing toilets, or if it is clean enough, dish washing and laundry.  A properly designed system can even produce drinkable water, but this gets more technical because of the obvious hazards for human health.  You would definitely need to look into local government regulations and work with an experienced professional for these types of systems.

In many parts of the world people have used low-tech rainwater collection systems like these successfully for generations.  There is no doubt that clean water is globally becoming scarcer every year, and so becomes more valuable and politically charged.  Especially in the case of a brand new home and garden, a rainwater harvesting system really should be part of your design, even if you’re just allowing for a future installation.

(some of these references include their own longer lists that I also drew upon):
Water Management, Occidental Arts and Ecology Center workshop led by Brock Dolman, fall 2012

Water Harvesting in California: Obstacles and Opportunities, published by The Water Institute at OAEC, www.oaecwater.org

Slow it. Spread it. Sink it., published by the Southern Sonoma County Resource Conservation District, www.sscrcd.org

Urban Farmer Store literature and website www.urbanfarmerstore.com

An rainwater tank supplier with a particularly informative web site is  www.supatank.com.au

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11. Patterns in Nature (part two)

I’d like to return now to talking about patterns in nature. Besides the Golden Section, branching patterns have fascinated me for a long time and I’ve always wondered if there are common characteristics among the many different branching patterns in nature. Besides plants, you see similar patterns in river systems, human blood vessels, bacterial colonies, and even electricity (lightning). Why are branching patterns so common?

The short answer is that a branching pattern is a very efficient way to distribute or collect something from a large area. A river system collects all the rain water that falls in a watershed and brings it together to flow to the sea. A tree distributes leaves out in a three-dimensional shape to collect as much sunlight as possible, while also dispersing nourishment collected from the soil. Blood vessels are moving blood around the body to distribute oxygen and nutrients. Since all these systems are made to do the same basic thing, is their structure based on similar principles?

Similarity of Branching Patterns
Certainly you can see some visual similarities between the patterns of a tree branching and that of a river system. Scientists from different disciplines have studied this in depth and think there are similarities, for example the hydrologist Luna Leopold has said that, “there appears to be an inherent economy in the structure of a branch network.”

An idea called the “principle of least work” has been put forth to explain one aspect of the similar branching structures in different systems. The concept is that branches develop in a way to minimize the energy used to keep fluids circulating. Where a branch occurs is said to be determined by to the ratio of the size of the trunk to the branch. If the branch is small relative to the trunk, then it is more efficient to keep the fluid in the larger artery as long as possible, so the branch would tend to be higher up and closer to a 90 degree angle. If the branch and trunk are closer to the same diameter then it would tend to be lower down and closer to a zero degree angle. This is essentially because the larger diameter means less friction per unit. (There is much more detail on the math and graphic studies behind this that you can find if you’re interested.)

This makes sense at an abstract level, but in nature we don’t see several trees in a row with exactly identical branch structures. There are many other factors that can influence the growth of each branch – sunlight, temperature, available energy and raw materials, proximity to other branches. Its easy to personify a tree and think of it as consciously putting out its branches to maximize efficiency, but in fact it is an ongoing trial and error process with the less successful branches withering and dying off.

Comparing tree branching to a river system, there are obvious differences, related of course to the physics of the space they inhabit – trees grow up against gravity to reach the sunlight, while rivers go downhill with gravity. Leaf veins branch out to distribute fluids but also divide the surface up into smaller cellular units and provide structure. Vascular systems exist within cellular masses with other forces acting on them. So, the short answer is that yes, there are conceptual patterns that underlie branching structures, but not to the point that you see precise similarities.

Branching Patterns and Landscape Design
Part of what I think is fascinating and inspiring about natural patterns is the infinite variety within an understandable general structure. Human built things tend to have much less variety, mainly because of the efficiencies of mass produced, standardized parts. It seems to me that branching patterns have the potential to add visual appeal to designed spaces in a lot of different ways. A building’s structure, the collection of a site’s rainwater, or the path system that brings people from their cars to the front door could all use branching structures. Let’s explore one possibility – the planning of neighborhoods – why do our cities tend to use grid-like patterns instead of branching ones?

One of the typical functions of a city’s roads is to distribute people from a central work and shopping area out to individual homes. The well-known architect Christopher Alexander famously said “A City is Not A Tree” but I had to see for myself. I drew a plan of a hypothetical neighborhood using a branching pattern, and even though it looks nice on paper, I realized that there really are efficiencies in a grid that aren’t equaled in a branching system. Most natural branching patterns flow in only one way, so when you are dealing with car traffic, the acute angle of a tree branch is not nearly as good as a 90 degree intersection for moving in any direction. Branches also naturally concentrate flow the further downstream you get, which in terms of roads means traffic jams. I had to add a bike and pedestrian trail network to connect between the branches for travel horizontally within the neighborhood; otherwise it’s a long walk to your friend’s house on another branch. So the branching pattern isn’t the best one for all situations, although I think this could be studied more.

Overall we see that branching type patterns are very common in nature, but their specifics vary greatly according to purpose, context and other environmental factors. They generally occur when there is a large area to distribute or collect resources from, utilizing smaller and smaller branches as they reach out to the periphery of the area. Ultimately these branching patterns often become fractal in nature – having similar pattern units repeated over and over at smaller and smaller scales. This is how I visualize root systems – you may not actually see roots in the soil when you dig, but there are very thin little tendrils woven in there, maximizing the ability of the plant to absorb water and minerals. Branching patterns are so common in nature that we use them as a conceptual guide for all kinds of thinking, from family trees, to computer directory trees. Maybe one day we will even be able to grow a building in the same way a tree grows its branches out!

Patterns in Nature, by Peter S. Stevens

On Growth and Form, by D’Arcy Thompson

Trees and Streams: The Efficiency of Branching Patterns, by Luna Leopold

A City is Not A Tree, by Christopher Alexander

Branches, by Philip Ball  (this is part of a great series of recent books that I’m just getting into – looking like the best, most current resource on this topic, so I may be updating things later!)

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10. Native Plant Communities

Its time to get into a third level of discussion about native plants appropriate for the home garden.  I have already written about the very macro level of Plants of the Mediterranean Climate Zone, and the traditional level of definition of California native plants within the California Floristic Province.  Now I would like to go to a more micro level and look at California’s Plant Communities.

What Is a Plant Community?
What’s this – plants live in communities? Indeed it is true, but not exactly like our human communities.  Certain plants associate together because they like the same soil, climate and other environmental conditions, and each fills a certain niche within these conditions to form a complementary grouping.  For example, we have the well-known Redwood Forest plant community, with its signature tree, the Coast Redwood (Sequoia sempervirens).  These trees live in valleys along the coastal fog belt, but not so close to the ocean to have significant salt air.  They obviously create a shady understory climate, and all the needles they drop to the ground form a very soft, nutrient rich surface.  The trees also condense and drip some of the fog-borne moisture into the soil, all leading to a great environment for ferns, mosses, and fungi.  Not all plant communities are this distinct, and in fact there is some disagreement about the usage of this categorization in the world of the plant sciences.  But for the purposes of learning what native plants will work well together, the plant community is a useful concept.

Plant Communities Common to the Bay Area
There are about 28 different plant communities in California that include everything from the Coastal Marsh to the Alpine Fell Field and various kinds of Forests, Woodlands, Grasslands and shrubby ‘Scrub’ communities.  For the less scientific purposes of finding plants to use in your yard, I prefer to simplify it down to the following ones common in Coastal Northern California:

    • Chaparral
    • Coastal Sage Scrub
    • Coastal Prairie
    • Valley Grasslands
    • Oak Woodland
    • Mixed Evergreen Forest
    • Redwood Forest

From this list you can determine the ones that were most likely to exist naturally in your area and narrow down the native plants that are likely to work well there.  You are also able to get closer to plants that would be truly native to your site, which makes more sense to me than being able to select anything from the entire California Floristic Province and call it a “native” plant garden.

A great example of the usefulness of this approach is gardening with a Coast Live Oak (Quercus agrifolia).  This is a beautiful tree that is a major feature of the Oak Woodland plant community, and is common to Bay Area climates and clay soils.  It is highly valued in gardens, but very sensitive to excess water that typical garden plantings need.  By looking at the other plants native to this community, you find those that naturally like these dry shade conditions, such as the bunchgrass California Fescue (Festuca californica) and the deciduous Snowberry shrub (Symphoricarpos albus).

Other Plant Communities
In addition to the common plant communities, it is also useful to be aware of the less common ones of the desert, wetlands, streams and rocky bluffs because their environments may resemble certain tough and/or unusual situations.  For example, the succulent Stonecrop (Sedum spathulifolium) and the flowering Seathrift (Armeria maritima) are native to the rocky bluffs of the coast and so become natural choices for use on green roofs with thin soil profiles that are near the coast.

Benefits of the Plant Community Approach
A few benefits of approaching your planting design in terms of native plant communities have already been mentioned – you are able to get closer to truly site-specific native plants, and you are getting plants well adapted to your local conditions.  Another great benefit is the excellent habitat you are providing for locally native birds, insects and animals, which naturally prefer the native plants they evolved with.  The connections you can make to the local natural environment are also exceptional when you are using the same plants that are found in your nearby open spaces and parks – you achieve a sense of place that connects you to the greater outdoors.

Limits to this Approach
Taking it one step further would be to attempt a true restoration of a native plant community by installing all the major plants of the exact community that existed on your property before human occupation.  This can be a good idea if approached judiciously, especially if you have a large area and live on the edge of an open space.  However, there are several reasons not to take the plant community approach too far.  First, the typical yard is not likely to represent the native environment exactly.  Developed areas that have been occupied for more than a few years will have modified soil, climate, air quality and ecology.  You also inherit plethora of weed seed that will be major competition for many types of native plants.

Another reason is that, at least up close to your house, you probably want your garden to look beautiful and hospitable year round. Not all plants native to a community are going to look great in a garden, and many look good for only a short time.  Because of our summer dry climate, many native plants go dormant from mid-summer until the winter rains begin, which could leave you with a brown garden of dried leaves and bare spots that might even be a fire hazard.

So it is important to be selective about which plants that you use from a certain native plant community.  It is ultimately a subjective, aesthetic decision, but I think it is best not to take the plant community approach too literally.  Consult your favorite Landscape Architect for knowledgeable design thinking on plants within a native community that will look great in your yard and take another step towards a more environmentally responsible garden.

Designing California Native Gardens, by Glenn Keator and Alrie Middlebrook

California Native Plants for the Garden, by Bornstein, Fross and O’Brien

Cal Flora web site www.calflora.org

A Manual of California Vegetation, Online Introduction, California Native Plant Society, http://www.cnps.org/cnps/vegetation/manual.php

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9. Landscape Sustainability: Stormwater

I’ve already gotten into what sustainability means to me and now it is time to talk about specific methods of landscape sustainability, with a focus on simple things that can be done in residential yards.  Let’s start by looking at all that fresh, clean water that falls from the sky, typically referred to by engineers not as rain, but stormwater.  When it falls on a paved surface, or a building roof, it is not able to immediately go where it would if us humans weren’t around – into the ground.  The traditional approach has been to get the stormwater from these impermeable surface into pipes as quickly as possible, but this has led to increased erosion, flooding, water pollution, and habitat degradation.

The sustainable approach is to take care of all the rain that falls on your land right there.  If you can, collect the runoff from your roof and store it for use, something I will talk about in depth later.  Otherwise you are trying to do three things with your stormwater, nicely put by the Sonoma Valley Groundwater Management Program: Slow it. spread it. sink it. By slowing the water down you take energy out of it that would cause erosion, and by temporarily holding it on your property, you keep the local streams from getting overwhelmed and flooding.  Spreading the stormwater allows dirt and other particles to settle out before the water gets into our streams, rivers and lakes.  Sinking the runoff into your soil follows the natural cycle and replenishes groundwater.  What are the ways you can do these things in your yard?

Pave Less & Make It Permeable
I can’t put it any simpler than the authors of Sustainable Landscape Constructionpave less.  Take away every square foot of concrete and asphalt that you can, and use permeable paving surfaces as much as possible.  There are many good material options to make functional but permeable pathways.  The most common are loose gravel or stepping stones that allow water to enter the soil in the gaps between – but these are for foot traffic or light vehicle use only.  For regular vehicle traffic one of the best options is a precast permeable paver.  This type of paver has built in spacers which create gaps for water flow while maintaining the necessary interlocking strength.  Other materials have been recently added to the list of possibilities including: permeable concrete (looks like rice crispy treats), permeable asphalt, soil reinforcing grid systems and even synthetic fibers directly in the soil that reinforce it enough to support vehicles.

With any permeable paving surface, it is critical to consider what is underneath it.  If you have clay soil, only a limited amount of rain water will be quickly absorbed.  In those cases a layer of drain rock can be placed under the pavers.  The gaps between the rocks store the water, giving it more time to sink into the ground.  This can require a pretty thick layer to do much good, and may become construction intensive and costly.  So, you’re probably better off turning to the other category of sustainable stormwater solutions: on-site infiltration in planting areas.

Rain Gardens and Bioswales
For a few square feet of impermeable paving, simply sloping to a planting area may be all you need to do.  However, for larger areas you want to be careful not to concentrate too much water into a single point in your garden; you will start to create erosion and even pollution problems.  Any surface where cars travel will collect the fluid drippings, particles from brake pads, etc, so the water that washes across these surfaces needs to be treated accordingly.

The Rain Garden or Bioswale is the typical approach to sustainably take care of your stormwater.  In my mind these two things are pretty much the same: you are creating a swale (a.k.a. ditch) or other depression designed to accept the stormwater without eroding. The stormwater gently flows into, then slowly across the swale, allowing for surface filtration by the plants as well as absorption by the soil below.  In addition to the particles that settle out of the slowed down water, plants and their associated soil organisms can break down pollutants, making the water cleaner (known as bio-remediation).

Again, with compacted or clay soils, you may not get much absorption, but you are still slowing and spreading out the water temporarily.  For larger scale projects, the clay soil is often removed and replaced with a special well-draining soil mix that provides additional filtration, but is connected to the storm drain piping downstream. I n all cases you need to be careful not to create a ponding situation where you have standing water longer than 72 hours – mosquito breeding becomes an issue – so always include an overflow outlet for bigger storms.

These bioswales can be made into interesting design features that earn it the more evocative Rain Garden title.  The extra moisture of the swale will create a nano-climate for unique plant types that will make it noticeable in your landscape.  Round river pebbles are also typically used as a mulch in place of bark chips, which will tend to float away.  This is a great opportunity to give visible expression to the natural process of water flow, an important part of sustainable landscape design, connecting us back to the natural world.

The control of stormwater runoff is a major issue in all urbanized areas and the State of California now has a set of stormwater management rules to address it, known as the C.3 Regulations.  New construction projects beyond a certain size require bioswales and other measures be installed to take care of stormwater within the property’s boundaries.  You have probably seen these required bioswales in the parking lot of your office building or shopping center without realizing what they were.  By capturing and controlling the rain that falls on your property you are not only making use of a valuable resource, you are improving your neighborhood’s ecology and keeping the regional watershed cleaner.  The only real question is why wouldn’t you do it?

Sustainable Landscape Construction, by J. William Thompson and Kim Sorvig

Water Management, Occidental Arts and Ecology Center workshop led by Brock Dolman, 2012

Water Harvesting in California: Obstacles and Opportunities, published by The Water Institute at OAEC, www.oaecwater.org

Slow it. Spread it. Sink it., published by the Southern Sonoma County Resource Conservation District, www.sscrcd.org/rainwater.php

Sustainable Sites Initiative Guidelines 2009, American Society of Landscape Architects, http://www.sustainablesites.org/report/

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