Landscape for Life - Water Workbook

1. LANDSCAPE FOR LIFE
TM
WATER
WORKBOOK

2. a c k n ow le d gements
Landscape For Life is a project of the United States
Botanic Garden and the Lady Bird Johnson Wildflower
Center at The University of Texas at Austin.
Landscape For Life is based on the principles of SITES,
The Sustainable Sites Initiative , the nation’s first rating
TM
system for sustainable landscapes (www.sustainablesites.
org), an interdisciplinary effort by the American Society of
Landscape Architects, the Lady Bird Johnson Wildflower
Center at The University of Texas at Austin, and the
United States Botanic Garden in conjunction with a
diverse group of stakeholder organizations. SITES offers
technical tools for professionals who design, construct,
operate, and maintain landscapes of all sizes. Landscape
For Life presents this information in an easy-to-use form
for homeowners and gardeners.
The information in this workbook is also available on the A sustainable garden in Texas
Landscape For Life website (www.landscapeforlife.org). includes a buffalograss lawn and
other native plants that nurture
Written by Janet Marinelli wildlife.
Designed by Elizabeth Ennis
Illustrations page 8, Sustainable Sites Initiative; page 10, Elizabeth Ennis
Cover photos, left to right: first two images, Bigstock.com, H. Zell, last two images, Bigstock.com. Photo
page i, Andy and Sally Wasowski, Lady Bird Johnson Wildflower Center; page ii, Steve Greer/VIREO;
page iii, public domain image via Wikipedia; page 1, Manual Broussard/FEMA; page 2, Ward Wilson;
page 5 public domain image via Wikipedia; pages 7 and 8, Nancy Arazon; page 11 left and right, Walter
Siegmund; page 15, Holly Shimizu
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3. I n t rod uc tIon
w o r kI ng w I th nature to create a
h e a lt hy, be autI ful home l andscape
Landscape For Life shows you how to work with nature
for a beautiful, sustainable garden, no matter where you
live, whether you garden on a city or suburban lot, a 20-
acre farm, or the common area of your condominium.
Conventional gardens unintentionally often work against
nature. They can damage the environment’s ability to
clean air and water, reduce flooding, combat climate
change, and provide all the other natural benefits that
support life on earth—including us.
The good news is that even one home garden can begin
to repair the tattered web of life. It’s possible to create a
great-looking garden that’s healthier for you, your family,
your pets, and the environment—and that saves you time
and money.
The Landscape For Life workbooks help you transform
your home garden into a beautiful and healthy refuge
for you and your family. You can download the complete
workbook, or individual workbooks on Getting Started, Soil, Water, Plants, Materials, and Human
Health. Each workbook includes helpful advice on gardening practices that take advantage of natural
processes at work on your property.
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4. c o n t ents
Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Create a water-thrifty landscape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Select plants adapted to local precipitation patterns . . . . . . . . . . . . . . . . . . . . . . . 3
Use alternatives to drinking water for irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
A guide to water-thrifty irrigation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Smart strategies for managing stormwater. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Create a rain garden . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Limit impervious surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
A guide to green roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Protect and restore vegetative buffers along waterways and wetlands . . . . . . . . . . .14
Sustainable water features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
iii

5. wat e r
So much of the earth is covered with water, it’s sometimes called
the “water planet.” About 97 percent of the water is ocean
saltwater. Most freshwater is locked up in the polar icecaps.
Only .003 percent of the earth’s water is available for human
consumption.
Water is chronically in short supply in arid areas, and can be
scarce even in places that historically have had a lot of rain. Yet
we often lavish it on our landscapes—typically drinking water,
which we pay a lot of money to treat and pump. Meanwhile,
instead of capturing and using rainwater in our gardens, we’ve
created an entire infrastructure of gutters, downspouts, and
sewers to get rid of it. The resulting stormwater runoff can
contaminate local waterways with fertilizers, pesticides, and other
Public water supply and
pollutants.
treatment facilities consume
The good news is that it’s possible to harvest enough non-potable enough electricity to power more
water to meet landscape needs and prevent polluting stormwater than 5 million homes for a year.
from running off our properties. In most cities, pumping and
treating water and wastewater
Information on selecting plants adapted to the precipitation accounts for 25 to 50 percent of
patterns in your area, alternatives to drinking water for irrigation, the entire municipal energy bill.
and how to irrigate efficiently follow. For details on using organic
mulches to conserve water, see the Soil workbook.
Conventional And Sustainable Landscapes: How They Compare
Conventional Landscape Sustainable Landscape
• Treats rainwater as a waste to be removed from • Manages rainwater as a resource to be used on
the site the site
• Can generate stormwater runoff that pollutes local • Designed to keeps stormwater on site and
waterways protect local waterways
• Usually irrigated with municipal drinking water • Irrigated with alternatives to potable water
• May result in high water bills • Can be cheaper to maintain
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6. cr e at e a water -t h r Ift y la ndsc a pe
Americans consume more than 7 billion gallons
of water a day outdoors. One to two thirds of the
drinking water we use is for irrigation.
It is a popular misconception that this is the only
way to have a healthy lawn and garden. A beautiful
landscape can be in tune with the amount of
precipitation that falls naturally in the area.
Sometimes irrigating makes sense. New transplants
need to be watched carefully throughout the first
year and watered when the soil dries out or the
plants look stressed. In arid climates, gardens may
go dormant and look brown in summer without some
supplemental water. Vegetables often require more
moisture than nature provides via rainfall.
Information on selecting plants adapted to the
precipitation patterns in your area, alternatives to
drinking water for irrigation, and how to irrigate
efficiently follow. For details on organic mulches and
how to use them as a water conservation measure,
see the Soil workbook.
Rainfall flowing off a home’s roof into a rain barrel is used to
irrigate the garden.
How Low Should You Go?
You can measure your progress against benchmarks used in the Sustainable Sites Initiative
(SITES) (www.sustainablesites.org), the new rating system for sustainable landscapes on which
Landscape for Life is based. SITES awards two points for gardens that reduce the use of potable
water by 75 percent from a local baseline case. Three points are awarded for gardens that use
no potable water for irrigation once plants are established, and a garden that consumes no
potable water both during and after establishment is awarded five points.
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7. SELECT PLANTS ADAPTED TO LOCAL
PRECIPITATION PATTERNS
Growing plants adapted to the conditions found on your property is one of the basic principles of sustainable
gardening. You’ll find a detailed discussion on how to choose the right plant for your site in the Plants workbook.
Following are some tips to help you create a garden that’s suited to local precipitation patterns:
• Preserve as many well established trees and shrubs as possible, because they generally require less water than newly
planted specimens.
• When selecting plants, avoid those labeled “hard to establish,” as they often require large amounts of water.
• Favor plants native to your region, which are adapted to the local climate. Be sure to choose native plants that match
the specific conditions at the planting site.
• If you’re considering a non-native plant, make sure it is not a known invasive species in your region. Some invasive
plants are water guzzlers and can transform the natural hydrology of natural areas, making it even more difficult for
the native species to survive.
• To speed establishment and minimize water use, plant at the recommended time for a particular species. They key
to successful transplanting is getting the roots to grow into the surrounding soil as soon as possible. For many plants
in areas with regular rainfall in the warmer months, this is in spring, when roots are growing most actively and there
is enough moisture in the soil to support new growth. In warmer areas, fall is a much better planting period, and
the best time to plant many woody species is when they are dormant in the winter. Consult plant labels or your local
nursery or public garden (http://www.publicgardens.org/gardens) about the best time to plant.
• The size of your lawn and what type of turf grass you grow can have a huge impact on the amount of irrigation your
landscape requires. Read more about creating a regionally appropriate lawn in the Plants workbook.
USE ALTERNATIvES TO MUNICIPAL DRINKINg WATER
FOR IRRIgATION
With a little ingenuity, you can use non-potable water from a variety of sources both indoors and outdoors to
irrigate your garden. Non-potable water is not fit for humans to drink, but is generally safe for plants. According
to the American Water Works Association Research Foundation, households that irrigate with alternative water
sources can slash their water bills by as much as 25 percent.
Rainwater Collection
Rainwater collected in barrels or other storage tanks has been used for irrigation for centuries. Rain barrels are
connected to the downspouts of a home’s roof gutters and typically hold around 50 gallons. They come with a
screened cover and an overflow spout and hose to divert excess water away from the home’s foundation. The
typical house has at least four downspouts, at each corner of the house, and rain barrels can be connected to one
or more of them. Of late, designers have been creating versatile variations on the rain barrel, including models
with sleek profiles that can fit along narrow passages, under decks, or in other underused spaces. Modular designs
enable you to add on capacity or even put the tanks in multiple locations.
Cisterns, storage tanks made of stone, mortar, plaster, or cement, were once very common in the U.S., especially in
rural areas where homes relied on private wells for water. Today, prefabricated cisterns are available in various materials
and sizes. A cistern is a more complicated undertaking but can store a lot more water than a rain barrel. Check with the
nearest Cooperative Extension office (www.csrees.usda.gov/Extension/) for information on the best systems for your
region and how to construct them.
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8. For More Information
Other useful resources on harvesting rainwater are U.S. EPA’s rainwater collection handbook (http://www.
epa.gov/npdes/pubs/gi_munichandbook_harvesting.pdf) and the American Rainwater Catchment Systems
Association (www.arcsa.org/content.asp?pl=6&contentid=6).
Many states also have resources on rainwater collection. See, for example:
Texas Water Development Board (http://www.twdb.state.tx.us/iwt/rainwater.asp)
Rainwater harvesting case study for Florida (http://www.harvesth2o.com/floridahouse.shtml)
Rainwater harvesting at North Carolina State University (http://www.bae.ncsu.edu/topic/waterharvesting/)
Collecting Air Conditioning Condensate
Condensate is produced when warm, moisture-laden air passes over the coils of an air-conditioning system. The
average single-family home produces 5 to 10 gallons of condensate per day.
Condensate is an attractive irrigation option for several reasons. It’s produced through the normal daily operation
of air-conditioning equipment. Unlike rain, which is sporadic and unpredictable, condensate is produced
regularly during the hottest months when the need for irrigation is greatest. Inquire about the components of a
condensate collection system at local home improvement centers and farm and ranch supply stores. For more
on collecting and reusing air conditioning condensate, see the Alliance for Water Efficiency website (www.
allianceforwaterefficiency.org/Condensate_Water_Introduction.aspx).
Water From Dehumidifiers
Water pulled from the air by dehumidifiers is a high-quality source of water for irrigation. Because the water
typically ends up in a basin that is easily removed for emptying, no additional equipment is necessary.
Graywater Collection
A variety of appliances and fixtures produce used water called graywater. An estimated 50 to 80 percent of
residential “wastewater” is dish, shower, sink, and laundry water. Because graywater often contains soaps,
detergents, shampoos, or other substances as well as bacterial and other pathogens, its use is regulated by state
and local governments (see below).
Graywater is most often recommended for subsurface irrigation of non-food plants. Graywater systems vary from
simple and low-cost to complex and costly. The simplest way to collect graywater is to plug the drain and employ
a bucket to transport bath or shower water for use outdoors. Another common practice (but illegal in some
locations) is to drain the washing machine directly onto outside vegetation. Sophisticated systems involve separate
plumbing for graywater as well as settling tanks and sand filters to remove solids and pathogens.
State And Local Regulations
States and local governments have different regulations on what kinds of graywater are permissible for use. Some
prohibit the collection of graywater entirely, so be sure to investigate what qualifies as graywater and whether any
restrictions apply in your area. A list of some states and municipalities with graywater policies can be found here.
(www.oasisdesign.net/graywater/law/index.htm)
Different Systems For Different Climates
Keep in mind that different alternatives make more sense in some regions than others. For example, harvesting
rain flowing off the roof in rain barrels or other storage systems may be cost effective in rainy climates, but in
parts of the country with dry summers, rainfall may be too infrequent to make them worthwhile. In these areas,
capturing condensate from an air conditioning system is a better option.
4

9. A gUIDE TO WATER-ThRIFTy IRRIgATION
Conventional irrigation practices waste a lot of water. Irrigating with traditional sprinklers or when it is hot or windy
leads to water loss through evaporation. Watering too quickly or too much leads to runoff. The goal of water-wise
irrigation is to reduce these losses but still supply as much water as is necessary.
What To Do
• Irrigate only when your plants need water.
How often to water depends on a number of factors, including what type of soil you have, the type of plants
you’re growing, whether your plants are established, the season, and weather conditions. Don’t irrigate on a
fixed schedule, which wastes water by providing it when your plants don’t need an extra drink.
Frequent, shallow watering leads to weak, shallow-rooted plants. Less frequent, deep watering encourages roots to
grow deep, where the soil stays moist longer.
• Use a rain gauge and/or soil moisture probe.
A variety of relatively simple tools can help you determine when you need to water. The simplest and most
inexpensive of all is a rain gauge to measure weekly rainfall. Soil moisture probes employing different
technologies are commercially available at varying prices. They measure the moisture level of your soil, giving
you a more precise indication of how much, if any, water your plants require.
Rain gauges and soil moisture probes should be used in conjunction with basic knowledge about how much water
various parts of your landscape require. For example, vegetables generally need more than established woody plants.
And even edible plants require less water when it is overcast and relatively cool than when it is sunny and hot.
• Hand water.
According to an American Water Works Association
(AWWA) Research Foundation study, manual
watering with a hand-held hose tends to conserve
more water than other irrigation methods.
If you are going to have an in-ground system, make
sure it is a drip system as it used the least amount
of any automatic system—but still 16 percent more
than watering by hand. In-ground spray systems used
35 percent more water than hand watering, and an
automatic spray system used 47 percent more.
• Use drip irrigation systems or soaker
hoses.
Drip irrigation systems deliver water through tubing
and emitters placed alongside your plants. The
emitters slowly drip water into the soil in a plant’s
root zone where it is needed, not in gaps between
plants where it is wasted. They also reduce water
loss due to evaporation, and the low flow rate
minimizes the potential for water leaching below Watering by hand conserves more water than any other
the roots or running off the surface. Drip irrigation irrigation method, according to a study by the American
can be used in vegetable and flower beds and Water Works Association. The same study also found that
drip irrigation consumes much less water than the in-ground
around trees and shrubs. spray irrigation systems used in most home gardens.
5

10. As the AWWA study discussed above shows, however, drip systems must be operated properly to be truly water-
thrifty. To maximize their efficiency, install climate-based controllers such as sensors that prevent the system from
turning on during and immediately after rainfall. Even better are sensors that activate irrigation only when soil
moisture drops below a pre-determined level. So-called “smart” or weather-based irrigation controllers take into
account a range of factors to determine when supplemental water is necessary, including temperature, rainfall,
humidity, solar radiation, and soil moisture levels.
Soaker hoses, which have perforations that slowly leak water into the ground, can also be efficient and effective.
If you’re in the market for a water-conserving irrigation system, it’s worth checking out WaterSense. (www.epa.
gov/WaterSense/) Sponsored by the U.S. Environmental Protection Agency, the program seeks to do for irrigation
products and services and plumbing fixtures what the Energy Star label has done for electric appliances. Irrigation
technologies and services that have been awarded the WaterSense label are listed on the program’s website.
• Use alternatives to potable water for irrigation.
Take advantage of the various sources of non-potable water around your home. See page 3 for details.
• Water your plants early in the morning.
Mornings are cooler, so water doesn’t evaporate as readily as it does in the heat of the afternoon. Evenings are
cool, too, but water sitting on leaves overnight can cause fungal diseases.
For More Information
The Irrigation Association website (www.irrigation.org/) has a section for consumers with tips on how to hire an
irrigation contractor, when an irrigation designer is necessary, and “smart” technology that saves water, time,
and money.
6

11. s m a rt s t r at e gIes for
man a g I ng s to r mwat e r
In a natural landscape, the soil and vegetation absorb
precipitation like a sponge. In developed areas,
however, much of the land has been paved over, and
the soil itself is often compacted and impervious. The
amount of rainfall exceeds the land’s ability to absorb
it, resulting in stormwater runoff.
Rainfall flows from our roofs to gutters and
downspouts, over compacted lawns and driveways
into roads, and down storm drains. In most older
cities this stormwater can overwhelm sanitary
sewers, sending raw sewage as well as runoff
carrying fertilizers, pesticides, motor oil, and other
pollutants into nearby waterways. Runoff also results
in less water infiltrating through the soil to replenish
groundwater supplies. For a comparison of runoff
amounts from different types of landscapes, from
woods and meadows to urban business districts, see
page 8.
A sustainable home landscape is designed to keep
stormwater on the property, minimizing damage to
waterways and aquatic life. The typical house has at least four downspouts, at each
corner of the house. Connecting rain barrels to one or more
On the pages that follow, you’ll find information of them not only captures water for irrigating the garden but
on stormwater management strategies such as also helps minimize stormwater runoff.
creating a rain garden, limiting impervious surfaces
in your landscape, and restoring vegetative buffers
along any wetlands and waterways adjacent to your property. You’ll also find a guide to green roofs. Collecting
rainwater that flows from your gutters not only provides an alternative to drinking water for irrigation but also
reduces stormwater runoff; see page 3 for details. It is important to use landscape materials that do not pollute
stormwater. For information on polluting materials and alternatives, see the Materials workbook.
7

12. RUNoFF AMoUNTS FRoM DIFFERENT LANDSCApES
.6 inches of .6 inches of
runoff runoff
2.4 inches 2.4 inches 1 inch of
of infiltration of infiltration runoff
2 inches of 1.6 inches of
infiltration 2.5 inches of
runoff
runoff
1.4 inches of
.5 inch of
infiltration
infiltration
Impervious Impervious Impervious Impervious Impervious
surface 0% surface 0% surface 0% surface 38% surface 85%
WooDS MEADoW RoW CRop RESIDENTIAL URBAN
AGRICULTURE (0.25-ACRE LoTS) BUSINESS DISTRICT
As development increases, so do soil compaction and impervious surfaces. Compacted soils, along with
driveways, roads, parking lots, rooftops, and other impervious surfaces, make it difficult for rain to infiltrate
into the soil, as in a natural setting. As a result, the more impervious surface in a landscape, the less infiltration
and the more stormwater runoff it generates. The illustration above shows the percentage of impervious
surface and the amount of infiltration and runoff following a 3-inch rainstorm for each kind of landscape.
8

13. CREATE A RAIN gARDEN
One of the most effective ways to prevent stormwater runoff in a home landscape is to create a rain garden.
Basically, a rain garden is just a strategically located low area where water can soak naturally into the soil. Like the
rest of your ornamental garden, it can be full of colorful plants.
Rain gardens have other benefits, too. They help protect your community from flooding. They protect local
streams and lakes from the many pollutants carried by stormwater as well as the physical damage it causes. By
increasing the amount of precipitation that filters naturally into the ground, they replenish underground water
supplies. And rain gardens also provide valuable habitat for birds, pollinators like butterflies and bees, and many
of the beneficial insects that help keep your garden healthy by keeping pest populations in check.
Following are some things to consider when planning a rain garden.
• Where to put it
Locate your rain garden either near the house to catch only roof runoff, or farther away to collect stormwater
from the lawn as well as the roof. A rain garden can also capture precipitation flowing off of paved areas. Keep
it at least 10 feet from your house to prevent moisture problems.
• How big?
A typical residential rain garden ranges from 100 to 300 square feet, but the time needed to dig the depression,
the cost of plants, and the size of your property will help determine how large yours should be. The size of a rain
garden that can manage most or all of your runoff also depends on what type of soil you have and how much
roof and/or surface area will drain into it.
• How deep?
A rain garden should be 4 to 8 inches below the level of the surrounding land.
Rain gardens such as this one in Seattle can be attractive elements of your home landscape. They can also provide valuable
wildlife habitat, especially when native species are planted in drifts of three to seven of each for maximum impact.
9

14. • When the soil should be amended
If your soil drains poorly, you may need to add a layer of sand or gravel at the bottom of your rain garden to
prevent it from becoming an ephemeral pond. If you have clay soil with enough rock or other aggregate, or you
have clay loam, the sand and gravel bottom is probably unnecessary, unless you want the water to drain very
quickly. If your soil is heavy clay, you may also need to amend it with sand and compost.
• How to connect it to a downspout
To direct stormwater from a downspout, bury a length of plastic pipe in a shallow trench that slopes down to the
rain garden, or create a grassy swale.
• What to plant
It’s helpful to think of a rain garden as comprised of three wetness zones: In the lowest zone, plant species that
can tolerate short periods of standing water as well as fluctuating water levels, because a rain garden will dry
grassy swale
porous soil
A rain garden should be 4 to 8 inches below the surrounding land. You can direct stormwater from a roof
downspout to the rain garden with a grassy swale, as above, or with buried plastic pipe. The soil in a rain
garden should be porous, so if you have heavy clay soil you may need to amend it with sand and compost. Rain
garden plants should be appropriate for your region and tolerate both wet and dry periods.
10

15. out during droughts or at times of year when precipitation is sparse. Species that can tolerate extremes of wet
soils and dry periods are also appropriate for the middle zone, which is slightly higher. Put plants that prefer
drier conditions at the highest zone or outer edge of your rain garden. To enhance the garden’s value as wildlife
habitat, plant native species in drifts of three to seven of each for maximum impact. After planting, apply a layer
of organic mulch 2 to 3 inches deep to keep down weeds and protect and enrich the soil.
• Maintenance
Although rain gardens require some initial effort, they are easy to maintain. Until your plants become
established, you’ll have to weed out undesirable volunteers. Leave the dormant plants standing over the winter
in cold climates to provide seeds and shelter for overwintering birds and butterflies. In spring you can cut back or
mow the stalks of herbaceous plants if you prefer a neat-and-trim look.
For More Information
Rain Gardens: A how-to manual for homeowners (http://learningstore.uwex.edu/assets/pdfs/GWQ037.pdf),
published by the Wisconsin Department of Natural Resources and the University of Wisconsin-Extension, contains
comprehensive, step-by-step instructions on all aspects of creating a rain garden “based on a goal of controlling
100 percent of the runoff for the average rainfall year while keeping the size of the rain garden reasonable.”
It includes a number of rain garden planting designs and plant lists for varying sun and soil conditions that are
especially appropriate for the Midwest.
An extensive list of plants (www.bbg.org/gardening/article/rain_gardens/rain_gardens_2) appropriate for rain
gardens and native to the eastern two-thirds of the U.S. and Canada, which was compiled by Temple University, is
available on the Brooklyn Botanic Garden website.
Your state or county Cooperative Extension office (www.csrees.usda.gov/Extension/) is also a good place to
seek information on rain gardens appropriate for your area. See the next page for some recommended Extension
publications.
Among the lovely native plants recommended for Pacific Northwest rain gardens are Nootka rose, left, and western
columbine, right.
11

16. “Adding a Rain Garden to Your Landscape” (www.umext.maine.edu/onlinepubs/PDFpubs/2702.pdf ),
University of Maine Cooperative Extension
“Rain Gardens” (www.csgc.ucsd.edu/BOOKSTORE/Resources/GS3%20Rain%20Gardens_8-10-09.pdf ),
Sea Grant California and University of California Cooperative Extension
“Backyard Rain Gardens” (www.bae.ncsu.edu/topic/raingarden/), North Carolina Cooperative Extension
“Rain Gardens” (www.water.rutgers.edu/Fact_Sheets/fs513.pdf), Rutgers University Cooperative Extension
“Rain Gardens” (www.sustainability.uconn.edu/pdf/raingardenbroch.pdf), University of Connecticut
Cooperative Extension
Rain Garden Handbook for Western Washington Homeowners (www.pierce.wsu.edu/Lid/raingarden/
Raingarden_handbook.pdf), Washington State University Extension Pierce County
For ideas on what to plant, you’ll find links to native plant societies of the U.S. and Canada here (http://www.
michbotclub.org/links/native_plant_society.htm). The Wildflower Center Native plant Database (www.wildflower.
org/plants) is another helpful resource.
LIMIT IMPERvIOUS SURFACES
Impervious surfaces are mainly constructed surfaces—rooftops, sidewalks, driveways, roads—covered by
impenetrable materials such as concrete, blacktop, and mortared brick or stone. But urban and suburban soils,
which are often compacted by intense foot traffic or construction equipment, are also highly impermeable. As
urbanization increases, so does the amount of impervious surface. Studies have shown that the pervasiveness of
impervious cover is directly related to the poor quality of many urban watersheds.
Because they prevent precipitation from seeping down into the soil, impervious surfaces are a primary cause of
stormwater runoff. Torrents of destructive runoff are generated as rainfall strikes rooftops and pours into gutters
and downspouts, picking up volume, speed, and pollutants as it rushes over paved surfaces and into storm drains.
What To Do:
Following are some of the ways you can reduce impervious surfaces to enable water to seep into the ground.
• Two ribbons of pavement with a low groundcover in between is a more porous alternative to a solid driveway of
concrete or blacktop.
• Use stepping stones surrounded by creeping groundcovers instead of continuous impermeable pathways.
• Opt for “dry laid” instead of “wet laid” or mortared patios and walkways. Set in stone dust or sand, these allow
some stormwater to infiltrate into the soil, unlike the impervious cement products typically used as mortar.
• Green spaces between patios, pathways, and other impermeable spaces can help prevent stormwater from
accumulating and running off your property. Plant a rain garden to capture stormwater runoff from your roof.
• Restore the structure of any compacted soil on your property, and take steps to prevent soil compaction
elsewhere in your landscape. See the Soil workbook for details.
• Various types of permeable paving, such as concrete products with a porous structure that allows water to pass
directly through, can be expensive but are worth considering.
• Some green roof systems can help manage stormwater and are worth considering if you’re in the market for a
new roof.
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17. A gUIDE TO gREEN ROOFS
Most green roofs currently being installed in North America are so-called extensive roofs that consist of four major
components: a waterproof and root-repellent membrane to keep water from leaking into the building, a drainage
system, 3 to 6 inches or less of lightweight growing medium, and vegetation that is adapted to the extreme
conditions on rooftops and requires little or no maintenance. Living roofs cost a lot more than conventional roofs,
but last about twice as long.
Green roofs help reduce the urban heat island effect—the difference in temperature between urban areas
and the surrounding countryside caused by the lack of vegetation and large number of paved and built
surfaces that absorb heat. Research (www.wildflower.org/greenroof/) at the Lady Bird Johnson Wildflower
Center shows that green roofs can be up to 80 degrees cooler than adjacent buildings with traditional roofs.
By insulating your home, they also can significantly reduce energy consumption and heating and cooling
bills. They filter pollutants, improving air quality in towns and cities. In urban areas especially, they can
provide valuable wildlife habitat (www.nwf.org/News-and-Magazines/National-Wildlife/Gardening/Archives/2007/
Green-Roofs-Take-Root.aspx). And they add aesthetically pleasing green space, reducing the monotony of
barren city skylines.
A green roof’s ability to manage stormwater runoff, however, has been debatable. The growing media used
on green roofs typically contain slow-release fertilizer, which can be carried away in excess stormwater runoff,
polluting local waterways and harming aquatic life. A 2009 study by the U.S. Environmental Protection
Agency comparing the quantity and quality of runoff from green and flat asphalt roofs concluded that green
roofs are capable of removing 50 percent of annual rainfall volume, although this varied seasonally from
about 95 percent in summer to less than 20 percent in winter. The study, which was conducted by the Penn
State Center for Green Roof Research, also concluded that green roof runoff did contain some nutrients, but
because the volume of runoff was reduced significantly, green roofs actually led to less nutrient pollution than
asphalt roofing. And the runoff can be directed from the roof to a rain garden, where the nutrients can help
nourish the plants.
The Wildflower Center found that some green roofs are better at reducing runoff than others. Researchers
compared the performance of six extensive green roof systems from six different manufacturers to each other
as well as to traditional non-reflective blacktop and somewhat cooler reflective white roofs at the Center’s
headquarters in Austin, Texas. Each roof was planted with the same 18 native species chosen for their wide
tolerance of both drought periods and saturation after rainstorms. The plants were provided with the same
amount of water for irrigation each week when rainfall wasn’t sufficient.
Compared to both conventional and reflective roofs, the green roofs were much better at preventing the
temperature of the inside air from spiking on warm days. Some of the roofs were able to capture a significant
amount of stormwater (80 percent of a half-inch rain event and 40 percent of 1-inch and 2-inch events),
but others were not significantly better in this respect than the white or blacktop roofs. What’s more, while
some of the roofs had nearly no adverse effect on water quality, others were worse than the typical suburban
lawn—the more fertilizer in the planting medium, the worse the water quality (and the faster the plant
growth), although water quality dramatically improved after the first growing season. In short, no one system
excelled at providing all the benefits often attributed to green roofs.
What To Do:
• Green roofs are substantial investments. Although they’re not space-age contraptions, building one isn’t simply a
matter of hauling potting soil and plants to your rooftop. It’s important to consult a landscape architect, engineer,
or roofing contractor with experience in green roof installation. A directory of accredited green roof professionals is
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18. on the Green Roofs for Healthy Cities website (http://greenroofs.org/index.php?option=com_comprofiler&task=us
ersList&Itemid=&limitstart=0&search=&listid=4&name=&company=&city=Chicago&state=IL).
• Determine why you want a green roof—whether it’s aesthetic value, habitat value, or its ability to save energy or
retain stormwater. Make sure that a green roof is the most efficient way to achieve your goals.
• If you decide to pursue a green roof, make the consultant or manufacturer you are working with aware of your
goals and ask which green roof system is most likely to achieve them.
PROTECT AND RESTORE vEgETATED BUFFERS ALONg
WATERWAyS AND WETLANDS
In undisturbed natural areas, waterways and wetlands are typically protected by adjacent vegetation. Grassland,
woodland, or wetland plant communities reduce runoff by increasing the land’s capacity to absorb stormwater.
Less runoff means less pollution of all kinds entering the water, including nutrients from fertilizers, pet wastes, and
other sources—excess nutrients are the primary cause of the algal blooms that rob oxygen from the water and kill
fish. Plant roots stabilize the soil and protect against erosion. The vegetation also improves wildlife and fish habitat
by providing food, shelter, and shade.
In many areas, however, the native vegetation has been removed and these important ecological functions have
been reduced or destroyed. In residential areas, turf grass often extends all the way down to the water, polluting it
with stormwater runoff carrying fertilizers and pesticides routinely used in lawn care.
In developed areas, vegetated buffers can fulfill the same important ecological functions as undisturbed waterside
vegetation. As the name suggests, these are thickly vegetated strips of land that protect waterways and wetlands
from polluted runoff and erosion. They also provide habitat for a variety of wildlife year round, including “stopover
habitat” for migrating birds in spring and fall.
Research shows that as the width of a vegetated buffer increases, its ecological benefits also grow. Buffers less
than 50 feet wide offer minimal protection, while those 200 to 300 feet in width improve water quality and protect
aquatic habitats. Vegetated buffers more than 300 feet wide can function as wildlife corridors and even harbor
imperiled and sensitive species.
What To Do:
• If your property borders a waterway or wetland, create a thickly vegetated and undisturbed buffer at least 50
feet wide. These riparian and coastal zones are often regulated, so contact local and regional government
agencies for information on appropriate vegetation buffers in your area.
• Do not use any pesticides or fertilizers—even organic fertilizers including compost—in a vegetated buffer area.
• Undisturbed buffers provide the best protection. If you need access to the water, create an elevated walkway
made from untreated wood to protect the vegetation as much as possible.
14

19. susta I na b l e wat e r fe at u r e s
From decorative fountains and tubs to pre-formed
pools and ponds, water features have become
popular garden amenities, and for good reason.
The sight and sound of water is relaxing, and may
promote stress reduction and healing. Wetland
plants can be spectacular, whether the delicate
water-lilies that float on the still surfaces of ponds,
the brilliant cardinal flowers that populate marsh
edges, or the carnivorous pitcher plants that grow in
spongy bogs. The sound of a cascading waterfall,
a trickling stream, or even a bubbling urn adds
another dimension to a landscape and can drown out
unwanted clatter. What’s more, water features will
attract birds and other delightful wildlife to your yard.
Countless tomes on how to create a water feature
have been published in recent years, but they almost
never tell how to construct a feature that conserves
energy and potable water.
What To Do:
• Use alternatives to potable water, such as collected
rainwater or air-conditioning condensate, in your
water feature; see page 3 for details. Systems are
now available that combine a rainwater harvesting This sustainable water feature uses rainwater channeled from
the gutter. When rainfall is sparse it becomes a dry creek bed.
and storage system with a decorative water
feature.
• Use solar recirculating pumps, which conserve water and are powered by a renewable source of energy.
• Consider using an ecological design approach, creating a water garden that includes plants appropriate for
local conditions and functions as a natural ecosystem. A streambed that goes dry for part of the year may be
appropriate in an arid area. An in-ground pond that mimics the natural zones of vegetation found in natural
ponds may be appropriate for a good-sized property in a high-rainfall area—complete with floating plants like
water-lilies in deep areas; pickerel weed, arrowheads, grasses and sedges that grow partially in water in the
emergent zone; and colorful wildflowers, shrubs, or trees found where the wetland grades into upland.
For More Information
The Natural Water Garden: Pools, Ponds, Marshes & Bogs for Backyards Everywhere(http://shop.bbg.org/mm5/
merchant.mvc?Screen=PROD&Store_Code=BGGS&Product_Code=BBG-NAT-151&Category_Code=BBG-NAT),
edited by C. Colston Burrell and published by Brooklyn Botanic Garden, takes an ecological design approach to
water gardening, with step-by-step instructions and recommended plants for the Northeast and Mid-Atlantic, the
Southeast and Deep South, South Florida, the Midwest and Great Plains, the Western Mountains and Pacific
Northwest, and California.
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20. ww w. l a nds ca p e f o r l If e . o r g