Whew! At last we are getting some serious rain in the North State this season. We all agree that rainwater is precious—so why do we try so hard to move it off our property? On city and suburban lots, we channel rainwater from roof gutter downspout to street gutter storm drain as directly as possible. We don't want rainwater pooling around our foundations or settling into muddy sumps in our gardens, so modern houses and driveways are engineered to clear the runoff. But why not capture that precious rainwater in the soil? “Slow it, spread it, sink it” is the rallying cry of this permaculture principle of rain capture, and with some fairly simple landscaping—small berms, swales, and basins that direct, detain, and filter water—we can invigorate our soil ecology, enhance our yard's aesthetic and habitat value, filter pollutants, and help relieve over-tasked city storm drains.
The goal of on-site rain capture is to allow water to percolate into the soil rather than to create holding ponds, which require more complex engineering (and can foster mosquito breeding). Any effective rain garden landscaping should discourage standing water and allow flow to infiltrate the soil within a day or two. This can be as simple as a gravel-lined trench (often called a French drain) leading from a downspout to a grassy meadow or planting bed. A more complicated retention basin might entail layers of soil, gravel, and sand designed for slow seepage. For the purposes of this brief introduction, let's focus on a versatile and relatively simple structure, the swale.
A swale is a shallow channel, bermed a bit on both sides, that lets gravity do the work of moving rainwater along a gently sloping course. The swale directs water away from structures and through a straight or meandering depression lined with river rock, grasses, or other vegetation that can tolerate periods of winter wet and summer dry (regional native plants generally fit the bill). A grassy, vegetative swale might be lined with cool-season native meadow grasses such as sedges (Carex species) or rushes (Juncus species) that thrive with winter moisture and go dormant over the dry summer. A rock-lined swale resembling a dry creek bed holds visual interest throughout the seasons. Water-loving plants can be sited closer to the flow, while more water-averse selections can keep their feet dry further up the banks.
In general, your rainwater collection surface should slope downward from the water source, or you can create a minimum 2% slope. Steep slopes can create erosion, so avoid orienting your swale down slope in such areas.
Locate your swale:
- At least five feet away from structures without a basement, or ten feet from structures with a basement.
- Away from septic systems and leach fields
- Away from a tree's crown or major root zone to avoid root rot
- In full or partial sunlight to support plantings
Anchor your artificial creek bed with larger stones, boulders, and deep-rooted plants such as deer grass (Muhenbergia rigens) and fescues (Festuca species). If space permits, larger shrubs can create a more dramatically varied look. Vegetation should be planted and at least partly established before the winter storms, so be prepared to irrigate in dry periods and through at least the first summer. Once well established, deep-rooted native plants will enjoy the cool season storm water and survive the summer heat.
The illustrations here depict a professionally-designed creek bed along the driveway of a family home in Chico near lower Bidwell Park. A DIY project could be smaller in length, width, and overall scale while still employing some of the elements that make this feature so delightful.
From a simple gravel channel to a dry creek to a more elaborate retention pond, the hardscape elements of a rain garden project may seem daunting without step-by-step instruction. “Coastal California Rain Gardens” published by University of California Agriculture and Natural Resources (UCANR), offers detailed information about planning, building, and maintaining a rain garden, along with plant suggestions and resource listings.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area, visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at (530) 538-7201. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us Hotline webpage.
All photographs by Alicia Springer. Additional information and plant names used in photos:
Plants that tolerate winter moisture and summer drought line the banks of the swale. Idaho fescue (Festuca idahoensis) and California fuchsia (Epilobium canum) are seen. A redwood (Sequoia sempervirens) is on a raised bank so rainwater can irrigate but not saturate the root area. The redwood will require summer watering to stay healthy in the Butte County climate unless it's near a perennial stream.
A dry creek rain swale in a suburban garden landscape. The swale, roughly 50 feet long x 10 feet wide, runs along a sloping driveway. Redbud (Cercis occidentalis), deergrass (Muhlenbergia rigens), St. Catherine's Lace (a buckwheat, Eriogonum giganteum), Santa Barbara daisy (Erigeron karvinskianus) and California fuchsia (Epilobium canum) are among the native species seen.
Boulders and deergrass (Muhlenbergia rigens) stabilize the slope and provide pleasing visual variety. Larger native plant selections screen the property. These include toyon (Heteromeles arbutifolia), mountain mahogany (Cercocarpus betuloides), deer grass, and redbud (Cercis occidentalis).
A decorative rain chain at the ‘headwaters' of the creek bed directs flow from the roof gutter. Note that the creek bed is directed away from the base of the redwood, which is on a higher bank.
West of St. Helena in Napa Valley sits a lovely garden surrounding a small house with a large porch and big picture window. I had an opportunity to speak with the owner, Glenn, about how this idyllic spot came to fruition.
Several years ago, Glenn and Anne purchased this home hoping to retire in the next few years. They saw the potential in an outdated but solidly built home in the perfect spot, along a country lane yet close to town.
They needed to renovate the house first, and then plan the garden. They launched their project by hiring a landscape and garden designer to help clarify their vision for the plot. Seven elements of good design guided their decisions. They needed to consider the function, site, hardscaping, microclimate, water management, plant selection and maintenance of their ideal home.
Function: The landscape designer asked questions to help determine which design would best support their interests and needs. Glenn and Anne were asked how they planned to use their garden. Did they plan to entertain? If so, where? Did they have any specific plants in mind?
The couple expressed a desire for an aesthetically pleasing garden that would also be water- efficient, sustainable, friendly to wildlife and care-free. In the front yard, which the public could see, they wanted an attractive landscape featuring plants with color, scent and texture. They also wanted to attract butterflies, bees and birds, and they wanted color in every season. The backyard was to be a place to contemplate, sit quietly, read a book and entertain.
Site: Since guests would park on the street, the home needed a walkway from the street to the front door. The couple parks their own vehicles in the driveway to the left of a house, so another walkway was needed from the front door to the driveway.
Hardscaping: When the project began, California was in the middle of a serious drought. To conserve rain water, a swale (a depression between slopes) and series of berms (an earthen embankment defining the swale) were added to the front garden to percolate moisture into the soil. A fountain was added for birds and butterflies and placed so that it can be seen from the front porch and window.
The backside of the house had several steps and levels. The homeowners decided to make the landscape two levels and use locally mined paving stones on the lower level to the creek edge. To protect the house from water, the paved area slants away from the house and toward the creek. Well-placed potted plants protect people from accidently moving to the edge of the creek.
Several trees were dug up. An olive tree was removed and given away. Two crepe myrtles were moved from the backyard to the front.
Microclimate: The front of the house faces south; the back faces north. With a southern exposure, the front tends to be hot in summer, making it a good site for plants that flourish with little water. The trees and boxwood hedges on both the east and west sides of the front garden create several microclimates requiring differing kinds of plants.
With its northern exposure, the backyard is cool and moist, with little variation in climate. It is ideal for water-loving plants.
Water management: Once the two levels were defined in the backyard, the grass was removed using the sheet-mulching method. In the fall, a plan for watering was devised. The design relies in two drip systems. The main pipes for the back were placed under the paving stones. Glenn chose a meter that he manually adjusts himself according to variations in rainfall and temperature.
Plant selection: As you enter the front walkway, the scent of night-blooming jasmine (Nyctanthes arbor-tristis), English lavender (Lavandula angustifolia) and mock orange (Philadelphus) greet you. At the base of the porch steps, pots of gardenia (Gardenia jasminoides), one on each side, add to the scent. Sun-loving California fuchsia (Epilodium) andmanzanita (Arctostaphylos spp) are among the plants that grow atop the berms that define the natural stone swale meandering through the garden. Both attract butterflies, hummingbirds and bees.
Below the boxwood (Buxus) are newly planted red-twig dogwoods (Cornus sericiae). In the corner below the porch is Anne's “conversation corner” shaded by the bloodgood Japanese maple (Acer palmatum). Other plants for the back garden include a fragrant flowering currant (Ribes sanguineum ‘White Icicle'), dwarf hydrangea (Hydrangea paniculata ‘Bobo') and prostrate rosemary covering the creek bank.
Maintenance: Anne and Glenn can keep up the garden themselves due to the low-maintenance design. When they need help for tasks like transplanting trees, they hire local people.
For an opportunity to be inspired and learn more, you can visit Glenn and Anne's' garden on Sunday, May 21. It is one of six Master Gardener-owned gardens featured on the U. C. Master Gardeners of Napa County's “Discover Garden Magic” tour. Purchase tickets online at
http://ucanr.edu/survey/survey.cfm?surveynumber=20204
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
Is the drought over? Not by a long shot. My well is at the same level as it was this time last year, so I will continue to conserve water. How do I do that? By growing drought-tolerant, native, Mediterranean-type plants.
I have been gardening with such plants for many years. Last summer was a test of how well they would do with no summer watering. I did not water at all over the summer and lost only one plant.
I have nine swales in my garden. A swale is a shallow trench used to harvest rainwater and slowly release it into the soil. Plants tap into this reserve when water is scarce. Swales conform to the contour of the soil and have berms alongside that can be used for planting.
Several natives that have done well in my garden are sticky monkey flower (Mimulus aurantiacus), lavenders of many types, bottlebrush (Callistemon), native iris, red-hot poker (Kniphofia ), butterfly bush (Buddleja), milkweed (Asclepias) and salvias. I have intentionally created a habitat garden with lots of room and bloom for birds, butterflies and bugs. Right now, my breadseed poppies are showing their beautiful red heads. I started these with just a few seeds, and they have re-seeded widely.
Some monkey flowers have sticky leaves; others do not. These plants are native to Oregon, California and Baja California. The flowers look like little monkey faces and come in a variety of colors. Many hybrids have been developed and the flower colors are outstanding. They bloom over a long period, survived all summer in my garden without water and are up and blooming now. The plants can reach three to four feet in height and can be trimmed back.
Lavender thrives in my garden. Last year some went to seed, and wind and birds spread the seed. Now lavender in many colors is sprouting in other areas. There is even a white one, and I guess I can thank the bees for that. I have never had white lavender before.
Bottlebrush is native to Austrialia. It can take the form of a large bush or tree depending on how it is pruned. I have a couple that I keep as low bushes.
The flower of the Pacific Coast iris (Iris douglasiana) is typically blue, but hybrids have many different flower colors. I have a beautiful white one. My Iris confusa ‘Chengdu' came from a Bay Area grower; it grows well in shade without any summer water. It is one of my favorites.
Salvias are native to many parts of the world. Every time I think I have all my favorites, new ones appear. One identifying feature of sage is its square stem. Some salvias tower over me (I am petite), while others stay low. There are more than 900 species worldwide, so I don't plan on collecting all of them. I only have one acre. Sage blossoms are spectacular, and the leaves are aromatic. I love to rub my hands over the leaves and then smell the fragrance.
I have many milkweeds in my garden. They are mostly drought tolerant, and bees and bugs love them. Milkweed is the only food source for the larvae of the Monarch butterfly, and I want to encourage as many of them as I can. The Monarchs in the western U.S. evolved with native milkweed; they lay their eggs on milkweed. Most milkweeds die back in winter and come up in spring with big, bright flowers. Their milky sap make the larvae taste bad to birds, so they leave the larvae alone.
When I visited Turkey, I saw breadseed poppies (Papaver orientale) everywhere, their red heads waving in the breeze. I also saw them in some of the countries on the Dalmatian coast. The seeds from these poppies are sprinkled on baked goods.
My two large habitat garden areas are filled with native plants and take less time and water then the lawn they replaced. Gardening with natives is a great strategy for creating a water-wise yet beautiful landscape.
Workshop: Napa County Master Gardeners will hold a workshop on “Oaks and Native Plants” on Saturday, May 7, from 9:30 a.m. to 11:30 a.m., at Skyline Park, 2201 Imola Avenue, Napa. Stroll Skyline Park and the Martha Walker Garden to view oaks in their native habitat. Discover what grows alongside and underneath oaks. Learn about planting under oak trees in your own garden, about caring for oaks and about Sudden Oak Death and other stresses. On-line registration (credit card only) Mail-in/Walk-in registration (cash or check only).
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
- Author: David H Alosi
by Penny Pawl, U. C. Master Gardener
Swales are ditches or trenches that catch rainwater for the purpose of conserving it in the soil. And if you top the swale with compost, you will gradually improve the water-holding capacity of the soil underneath.Most swales are created on hillsides to keep rainwater from washing downhill, but mine are on the Napa Valley floor. They are not straight but rather bend around the plants already in the area. They are about two feet wide and 12 to 15 inches deep. Compost was spread on top of the soil including inside the swale.
Last winter, rains filled the swales up three or four times. Each time, it took about three days for the water to be absorbed and stored under the swale. I have been planting a dry habitat garden in this area. Eventually, these drought-tolerant Mediterranean plants, which have been in the ground only one to two years, will be on their own, with no additional water.
Because my plants were young, I watered every few weeks this past summer. A slow-growing Hollywood juniper that had been in the ground for a long time, with no water, doubled in size this past year. I can only presume it is because of the additional moisture provided by the swale.
As the roots of the plants go deeper and I continue to add compost on the surface, the water-holding capacity of this area should increase.
Last winter I placed a couple of garbage cans under downspouts, covering the cans between rains. I used this water on potted plants throughout the winter. Since then I have acquired two 300-gallon plastic containers. They rest on a raised platform under rain gutters, so after they fill, I can attach a hose and get some water pressure.
Because of the West’s growing water shortage, people are devising more ways to save rainwater. Some methods are elaborate, while others, like mine, are simple and inexpensive.
You can buy adapters to cut into gutters to direct the water and flat-sided tanks that butt up against the side of your house. These tanks are lidded and usually made of dark plastic so that light does not get inside. If kept covered, the water stays clean and free of mosquito larvae.
So how much rainwater can you glean from your roof? Most roofs are pitched, so a 1500-square-foot house may have a roof with double that surface area. In that example, an inch of rain will produce 1000 gallons.
To see how much rainwater you can save, check the chart at www.rainwater-green.com/RainfallCharts.pdf. Driveways, parking lots and streets also displace rainwater. In our area, any water not retained likely ends up in the river and bay
Some states do not allow collection of rainwater. Others allow limited collection to protect the interest of those downstream. California does not restrict rainwater collection, so you may harvest what you can.
Of course you can also save on water use by selecting plants that tolerate our dry-summer climate. When choosing plants, check their water requirements. You can also make plans to start eliminating lawn as that patch of grass is the biggest water user you have.