Greywater and Native Plants

17 June 2015 Prev Next

Don't you wish you could reuse some of your shower and laundry water to keep your landscape greener? Collectively, these are known as greywater, and the idea is so popular that the Santa Clara Valley Water District offers a rebate for laundry to landscape (L2L) greywater installations. Still, “greywater is not the first thing” to do, according to landscape architect Sherri Osaka, who spoke at a recent Gardening with Natives meeting. It's number 5 on the list, after these more crucial water-saving measures:

conservation: use less water whenever possible
check for and fix leaks
“get rid of the lawn!”
install natives, herbs, and edibles: drought-tolerant natives and many herbs require little or no water once established, and edibles offer a good return on investment

The L2L system, which is the easiest greywater modification, does not require a permit and offers the best payback. Since laundry water is “about 21.7 percent” of household water use, this simple system recaptures a significant amount for landscape use. Reusing water from sinks and showers is much more expensive and complicated, and is best plumbed in new construction or as part of a remodel. If you install a L2L system, you have to use a liquid laundry soap that does not contain borax, salts (sodium), or chlorine bleach, and you cannot use water that has been treated with water softeners. Avoid sending greywater to plants that need acid soil (blueberries, rhododendrons) or that can't tolerate recycled water (redwoods). Greywater cannot be stored. You install a valve so you can divert the laundry water either to your landscape or to the sewer as needed. The washer's pump moves the water to the landscape, using 1-inch PVC, PE, or Blu-Lock irrigation tubing, where it is released into mulch basins surrounding the plants. The mulch must be at least 2 inches deep, and the basins must be large enough so that the greywater spreads out and never comes to the surface. The California plumbing code also prohibits runoff and contact with groundwater. This kind of flood irrigation is best used for fruit trees as well as riparian natives and others that tolerate moist conditions. It's also approved for above-ground vegetables (but not root veggies). Natives that can be watered with greywater include the following. (Thanks to Deva Luna of Earthcare Landscaping for providing the list.)

Trees: alders, California sycamore, aspens, California bay, California fan palm
Shrubs: spicebush, creek dogwood, pacific wax myrtle, western mock orange
Berries: golden currant, elderberry
Grasses: pacific reedgrass, red fescue, deergrass, alkali sacaton, cattails
Sedges, rushes, and horsetail
Groundcovers: wild ginger, redwood sorrel
Perennials: golden-eyed grass, Pt. Reyes checkerbloom, hooker evening primrose, seep monkeyflower, stream orchid, mugwort, western columbine

Oh, and by the way, all other household water is blackwater: defined as toilet, dishwasher, and kitchen sink water, as well as laundry water if used for diapers. The California plumbing code does not allow blackwater to be reused. For more information on greywater, Osaka recommended Greywater Action classes and webinars, books and dvds by Art Ludwig from Oasis Design, and tours and classes at the Berkeley Ecology Center and EcoHouse.

Tanya Kucak conserves water by eating low on the food chain and collecting shower warm-up water in buckets.

Redwood sorrel is a well-behaved low groundcover for shady spots. Though its tangy leaves are rarely added to salads, it's best used as an ornamental if it's watered with greywater.

Western columbine does best in rich soils with moderate water. Using greywater will help it thrive without affecting your water budget.

Western mock orange likes rich soil. This large shrub can take infrequent watering, but thrives with moderate watering provided by greywater as well. It flowers profusely with fragrant white flowers from late spring to early summer.