HOME / gardening: All things green.

On Dry LandHow to plant a drought-resistant garden.

By Constance CaseyPosted Friday, July 27, 2007, at 6:51 AM ET

(Continued from page 1)

RSS

Perennials, even the prairie and desert ones, do have to be watered thoroughly when they're planted. Last weekend I saw a woman filling the back of her station wagon with about a dozen achillea (aka yarrow, often first on the list of drought-tolerant plants) with lovely terra-cotta colored flowers.

"So, I don't have to water these at all, right?" she called in parting to the nurseryman, who kind of nodded as he moved on to another customer. I suppose it's a good thing that I restrained myself from running after her car, yelling that newly planted perennials don't have a big root system, that they need a lot of water at planting time and attentive watering through the first year until their roots have matured and spread out. It's a complex message to get across while appearing to be a deranged person running down the road.

The achilleas at the home of the woman at the nursery may well be wilting right now, their nice ferny gray leaves sagging limply; she may be considering calling the nursery and asking for replacements. Roots have a hard time making contact with dry soil; watering at planting makes the soil stick to the roots and gets rid of air pockets where a root might dangle. Here is a gift to Scrabble players, a word likely to be mocked and challenged—turgor. To exhibit turgor means to be in a state of distension. From the Latin turgidus, swollen, inflated. (From which we have derived the idea of turgid prose—inflated and, thus, pompous.)

When the roots encounter a dry place, a hormonal message travels to the leaves to close their pores to slow down water loss. The pores, called stomata, are usually on the underside of the leaf. Squash and cucumber plants, which have pores on both sides, are extremely sensitive to lack of water; veteran vegetable growers use them as the canaries in the coal mine. Plants owe their capacity to be erect to water pressure; with less water in the system, they grow limp.

Which takes us to a much bigger picture. Scientists are working to make food crops that aren't adapted to arid places better at surviving drought by making their roots more efficient. A team of scientists headed by Roberto A. Gaxiola at the University of Connecticut has discovered a way to manipulate plant genes to increase root proliferation. Many naturally drought-resistant plants, especially the grasses of our great prairies, develop deep and dense root systems. It's a new idea; roots haven't previously been targeted in genetic engineering. Deeper, wider roots can spread out to more territory in search of water. The point, Gaxiola said, is to help agriculture in arid regions—Pakistan, Africa, China, and his native Mexico, not to mention Alabama.

In the past we've coddled our crop plants, giving them lots of fertilizer and water, things we used to think were unlimited. Gaxiola is aware that not everyone is on board with the manipulation of plant genes: "We are the witches of our time. People who don't understand the science would like to burn us."

Instead of being burned by drought, home gardeners, track the conditions in your area here and here, and check out these suggestions of plants that can thrive in gardens wanting for water. There's nothing wrong with praying for rain, but consider how nature keeps the soil moist—plenty of mulch, no bare earth.