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Getting drought-resistant plants off to the best start.

You've got to be careful when planting drought-resistant plants such as those we describe starting on page 74; the relationship between their roots and the soil is critical. Their planting needs are different from those of ordinary garden plants.

First, there's one and only one season for planting low water users-and that season is right now: after summer's long, hot days have gone and before winter's long, cold nights arrive. To establish the root growth that will sustain them through dry summers in years to come, drought evaders need winter's many months of low light intensity and (we hope) wet soil.

Check your soil's drainage Most drought-resistant plants need good drainage. You can check your soil for that before you plant. Dig a test planting hole and fill it with water. If it drains quickly, fill it again. If water remains after 6 hours, take steps to improve conditions.

If drainage is slow, use a post-hole digger to make a "chimney drain," a narrow hole about 6 inches in diameter, at the bottom of the planting hole. With luck, that hole will connect to a layer of more porous soil within a couple of feet. If it does, fill the chimney hole with fine sand or pea gravel, then plant as directed here.

If you don't reach a water-permeable layer, consider planting in a raised bed or in a mound of soil. Or perhaps rethink your plant selection or your landscaping scheme,

Amending soil that needs it

You need to amend your soil if you have no topsoil or if it is heavy, slow-draining clay or fast-draining sand. If you're planting a large area, spread over the soil a 2to 3-inch-deep layer of composted organic amendment and blend it with the soil to a depth of 6 to 8 inches (the cultivating depth of a spade or rotary tiller). Use the same proportion of amendment for backfill in the planting holes.

If you have well-drained topsoil, you probably don't need to use any amendment; adding it can create a barrier to both water movement and root growth. Once soil is prepared, follow steps I through 7 as shown here.

How to water drought-tolerant plants

Once established, many drought-tolerant plants can sustain themselves on rainfall alone. But whether that happens and how long it takes depends on the kind of plant and its exposure, your climate, your soil, and how the weather acts.

If you live near the coast (as in Sunset climate zones 15, 16, 17, 22, 23, or 24), it is quite possible to establish and sustain many drought-tolerant plants by watering through the first dry season and then letting winter rains take care of things.

But if the circumstances aren't favorable, some of these plants may need water through their second and third, and maybe even their fourth, summers. If winter rains are light (10 inches or less), or if rainy periods are widely spaced, you'll also need to water established droughttolerant plants during the winter. Typically, in a dry winter, one watering around

New Year's Day is enough. As a general rule, once plants have tripled i n size they are most likely established, and you can begin to reduce watering. To water by drip

If you need to water, drip-irrigation systems are best. They apply water exactly where it is needed, and slowly enough so it can soak in. Unlike flood or hose watering, drip watering never forces all the air out of the soil. Airless soil is fatal to some drought-tolerant plants.

When you water a 5-gallon-size plant, use three 1/2-gph emitters; leave them on for about 2 hours, always in early morning.

During summer, it is very important to avoid watering plants (such as ones marked with a * in the lists starting on page 76) during the hot part of the day. Water in warm soil promotes root disease. As plants grow, move the emitters farther out. As much as possible, try to keep the emitters just outside the drip line, at about the same distance from the plants' outer branches as shown in step 7.

To water by hose

If watering with a hose, make a basin around the plant. Make its inside edge over the edge of the original rootball, fill with water after planting, then follow the watering regime recommended at left. Each spring, make the basin larger to stimulate the roots to spread out.

More midyear water in the interior

In hot interior climates, many droughttolerant plants respond favorably to some irrigation during every dry season. It makes the plants grow bigger and leafier than they would with no midyear water. But carried to an extreme, such maintenance could have you saving little or no water with drought-resistant plants. Verdancy versus summer water use is a balance you'll have to strike on your own. top, and the wall slopes in against the hill as it rises.

One of the most useful retaining walls in the garden is also one of the smallest. The garden's original landscaper had poured fill dirt over the roots of a large Douglas fir. Knowing that even a foot of soil can smother roots and cause crown rot, Mr. Patton pulled the soil back a few feet around the crown and built a stone tree well. Ten years later, the tree is still healthy.

Walls for flood control

On the other side of Portland, George and Gwen Sumpter also faced a new landscape. Their problem was a hill that drained an orchard literally into the back of their new house.

They had a bulldozer terrace their rear garden so the water would be diverted around the house. To keep the terraces intact, Mr. Sumpter fronted them with dry rock walls, which hold the earth in place but let water seep through. The results-Mr. Sumpter's first try-are shown on this page.

At the bottom of the main terrace wall, he built a foot-wide, 14-inch-deep channel to carry runoff around the sides of the house. Stone for the walls is mostly brick-size "pit-run" (unsorted) rock from a local quarry. The walls have no formal foundations, but the base of the tallest one is buried about a foot below the floor of the drainage channel.

Behind the rock face, three horizontal bands of concrete also help support that tallest wall. Strengthened with reinforcing bar, each band is about 10 inches high, 10 inches deep, and runs the width of the wall. Because there's plenty of space between the bands, water can still get through.

The Sumpters keep their walls weedless by spot-spraying.
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Copyright 1988 Gale, Cengage Learning. All rights reserved.

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Date:Oct 1, 1988
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