Ollas and other tricks to save water gardening

This year, California, and Sonoma County in particular, is dry land. The U.S. Drought Monitor classifies the drought here as “exceptional,” the most serious of all categories of drought.

That means each of us should do whatever we can to conserve water, especially in the garden and landscape. After describing how you can conserve water while growing edible crops, we’ll cover ways to manage irrigation this summer for existing ornamental plants and landscaping.

Three principles are important for conserving water in gardens and landscapes. First, give plants only the water they need to survive until fall’s rainy season returns. Second, as much as possible, water each plant’s roots directly instead of wasting water on large sections of ground. And third, collect and use household water to water plants in pots that ordinarily would go down the drain.

Start with the food garden

About 50 years ago, an African farmer — whose name seems to have been lost to modern search engines — was living in a dry part of that continent and invented a super-efficient way to use very little water to grow healthy crops.

His method was simple and was recreated in dry lands around the world. It involves opening up a trench in easily worked garden soil about a yard wide and just as deep. Make it as long as you want, but 15 feet is a typical size. If it’s beyond your capacity to dig, hire workers or someone with a backhoe.

Fill the bottom of the trench with about a foot of organic matter such as weeds, grass, kitchen scraps, farm animal manure or anything that will rot. Cover this with a few inches of soil. Wet this down to encourage rotting.

Now, mix good compost with vermiculite 50-50 and add a foot of this to the trench. Wet it thoroughly. Vermiculite is an absorbent material that holds water. Spongy compost holds water, too, and supplies nutrients. Add another few inches of garden soil on top. Fill the trench with the compost-vermiculite mix to within a few inches of ground level, water it in well and cover the top with a mulch of grass clippings, dried leaves or peat moss to prevent evaporation.

This trench will hold water all summer, with maybe one August watering, if needed, to carry it into fall. You can plant summer crops like tomatoes, eggplant, okra, peppers and beans and fall crops like peas and lettuce. Tuck culinary herbs among the crops. It may not be as big as your regular food garden, but it will require far less water.

For the plants in pots on your deck or in your home or landscape, use gray water from your sinks by furnishing each bathroom sink with a plastic tub. When you wash your hands, brush your teeth or shave, you can tote that water to your potted plants. Rather than let bathwater or shower water go down the drain, close the drain and when you’re finished, use that water for potted plants.

Ordinary soap will not hurt plants. Consider diverting your washing machine water (as long as you’re not using bleach) into 5-gallon buckets with strong handles. Better to water plants with it than let it run down the drain. Tub and washing machine water can be poured on the root zones of ornamental shrubs to keep them going this summer.

If this is beginning to sound like a lot of work, it really isn’t. It just means working water conservation into your daily schedule. It also will decrease your water bills.

Bury pots

If you have overhead sprinklers delivering water to your landscape, consider changing to drip irrigation that delivers water directly to an individual plant’s roots. Drip irrigation systems, where ¼-inch plastic hoses are fed by main ¾-inch water lines, will keep your shrubs alive with an absolute minimum of water.

In the food garden, use soaker hoses laid so their loops are 18 inches apart to keep the beds moist without over-watering. These are perforated to let water slowly trickle out. Mulch applied over the hoses helps conserve water, too.

If you have groups of shrubs like roses, find a place to bury an olla among them. Ollas are porous clay pots you bury in the ground among groups of woody plants, then fill with water. The water slowly seeps through the clay, where plant roots will find it and curl around the pot to keep in touch with the moisture. Ollas really cut down on water use.

“They’ve been growing in popularity,” said Nina Gerety, who has carried them for years at her shop Potter Green & Co. at Cornerstone Sonoma.

She currently carries handmade ones by Napa potter Debra Manfree.

“Olla is an ancient form of irrigation used in all the arid parts of the world. They were used by Native Americans and in Egypt,” she said. Ollas use about 40% less water even than a conventional drip system.

“The soil stays perfectly balanced, perfectly moist. It’s not getting soaked and then drying out and then getting soaked again,” she said.

She has them in two sizes: a 13-inch olla that holds 2 quarts for a typical small raised bed and a smaller 1-quart size for containers ($45; $18).

The Petaluma Seed Bank, which just reopened after more than a year of being closed, has smaller container-size ollas in stock and is anticipating getting larger ones from Dripping Springs, a clay pot maker in New Mexico (drippingspringsollas.com).

Virtues of vermiculite

You know those 5-gallon plastic pots with drainage holes in the bottom that young woody ornamentals come in? Bury them up to the rim in your garden and fill them with that 50-50 mixture of compost and vermiculite. Then plant a tomato in each one, or three okras, eggplants or pepper plants. When you water, only water inside the rim of the pots. Mulch the surface with leaves or straw to reduce evaporation. Burying them keeps the soil cool and reduces evaporation.

Beds of annual flowers require a lot of water, compared to perennials. Consider forgoing them this year or plant them in pots instead that you can water with recaptured water from the tub or sink.

Lawn grass is also one of the thirstiest crops you can grow. It can only be irrigated with overhead sprinklers, so you lose a lot of water to evaporation. Think this year about replacing your lawn with water-conserving ground covers. You don’t have to give up grasses, but we don’t live in the well-watered East. Buffalo grass, blue grama grass, sheep fescue and white clover are all low-water alternatives to Kentucky blue grass and its ilk.

Perhaps the best alternative to lawn grass is yarrow, kept mowed at about 2 inches tall. Once established, it’s soft, takes foot traffic, is drought-resistant, needs no fertilizer and needs far less mowing than grass. And it’s pretty.

For further information, see what the state of California recommends by visiting suscon.org/california-water-guide.

Jeff Cox is a Kenwood-based food and garden writer. Reach him at jeffcox@sonic.net.