Water wisdom

Managing garden irrigation saves dollars and makes sense

November 2000

By Sharon Cohoon; Photographs by Bob Wigand
Sunset Magazine

Contrary to common opinion, a water-efficient garden is not all cactus and decomposed granite. It can be English cottage, formal French, Italian Riviera, or Southwest chic. Even roses and tropicals are possible in a water-conserving garden. "Water management is a very flexible system," says Tim Barr, technical services coordinator for the Western Municipal Water District in Riverside, California. "You don't have to forgo thirsty plants. You just have to budget for them."

Getting the most out of your water allowance is a matter of following a few basic principles, says Barr. The garden of Nan and Bob Simonsen in Riverside is one of his favorite examples of these principles at work. Though the garden has been a stop on public garden tours regularly since 1997 and won first place in the individual gatefory in the 1999 Water Efficiency Awards Contest, the Simonsens are relative newcomers to gardening, proving water-wise gardening is a learnable skill. "We visited the district's demonstration garden so frequently and took so many of their classes, I think we learned by osmosis," says Nan.

The Simonsens' property is quite large-2.75 acres. The thirstiest plants, including a lawn and rose garden, are confined to small areas close to the house, while plantings farther away thrive on much less water. A large slope drops down into a natural riparian area where Mediterranean plants grow. The slope on the other side of the riparian basin is planted entirely with California natives that, once established, will need little water beyond what nature provides.

Scrimping on the outlying areas saves irrigation money that can be spent on water for plantings near the house.

Water Management

LIMIT TURF. Turf grass is one of the thirstiest plants in our landspace. But that doesn't mean we have to eliminate it entirely. "There's really no satisfactory substitute," Barr says. Just limit turf to places where it serves a function, he says. On the Simonsens' property, only a tiny wedge near the front entrance has been planted with grass. "We put it in primarily for our dogs," Nan Says, "but it also provides a cool welcome."

GROUP PLANTS WITH SIMILAR WATER NEEDS. From an irrigation standpoint, this approach makes perfect sense. If plants that need to be watered at the same frequency and for the same length of time are in the same place, you can dedicate a separate line or valve to them, delivering exactly the amount of water the plants need and no more. Plants such as rosemary, lavender, and pride of Madeira, which have adapted to rain-sparse Mediterranean climates, do best when they receive slow, deep, and not-too-frequent soaks. Forcing these plants to share the same irrigation valve with turf grass, which needs shallow and frequent watering, is not just wasteful, it shortens the lives of Mediterranean plants and can even kill them. Overwatering causes the demise of more plants than anything else.

Here's how the strategy plays out in the Simonsens' garden. Nan's biggest watering indulgense is her English flower garden near the house. The roses in this area are on a drip-irrigation system. However, the rest of this area, planted primarily with perennials and annuals, is watered with rotary-head sprinklers because this part of the garden changes significantly from season to season and year to year. "The flower garden is my area to experiment," says Nan. The English flower garden is watered twice a week during the hottest months.

The sunny hillside leading to the riparian habitat, which is planted with mediterranean and other less-thirsty shurbs, trees, and perennials, is irrigated by impact-type sprinklers that put out water very slowly, minimizing runoff. Nan gives the plants about 1.5 inches of water per irrigation period. During the hottest months, the area is watered once a week. When temperatures drop below 90 degrees, the Simonsens stretch out the intervals between waterings.

The slope on the other side of the riparian area is only watered once a month-even in the worst summer heat. When the oaks and sycamores planted here mature, creating more shade, the slope will be self-sustaining and an irrigation system won't be necessary.

"Though every garden is a little different, putting your thirstiest plants close to the house and using less and less water as you move away from it is a very sound approach," says Barr.

IRRIGATE EFFICIENTLY. Through drip-irrigation systems get all the press, they're not the best solution in every instance, says Barr. "You need to match the system to the situation, the soil, and hte plants, as the Simonsens have done," he says. There are many factors to consider: drip-irrigation or underground systems, rotary or spray heads, output rates, and emitter sizes. Make your decisions based on research. Take advantage of the watering classes offered by your area water district. Talk to irrigation specialists, neighbors, and gardeners. Two booklets by Sunset can help. Water-Wise Gardening for California includes planting plans and plant lists. How to Water Your Garden explains options in watering systems and devices. To order, send $3.50 per copy to Sunset Water Booklets, 80 Willow Road, Menlo Park, CA 94025.

PLANT TREES. Plants under trees need less water because the shade lowers the air and soil temeratures, reducing moisture loss. (People are also cooler under these leafy canopies.) Properly placed trees can reduce air-conditioning costs up to 40 percent, according to Southern California Edison. Yet, surprisingly, shade-tree planting is one of the most neglected water-conservation techniques. Not at the Simonsens': They surrounded their back patio with trees. (Western and southern exposures, like those here, particlarly benefit.) The Simonsens added trees to their native and Mediterranean slopes. As the trees mature and shade more of the property, the Simonsens' irrigation usage will continue to decline.

IMPROVE SOIL; ADD MULCH. The Simonsens do both. Adding organic ammendments to the soil improves its texture, enabling it to make a better use of water. Giving soil to a 3 to 5-inch layer of mulch helps conserve water by reducing water evaporation.

Though these principles were all new concepts to the Simonsens just a few years ago, now they're second nature. Practicing water-efficient gardening has taught them to be more successful gardeners, Nan Says. Both Simonsens are now trained master gardeners with the University of California Cooperative Extension, and Nan teaches classes in gardening basics with an emphasis on wise water use through Riverside Community College.