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Published: Thursday, April 7, 2005, SEATTLE POST-INTELLIGENCER

http://seattlepi.nwsource.com

Rain or no, think drought-tolerant plants

By Ann Lovejoy
SPECIAL TO THE POST-INTELLIGENCER

Despite the rains, we can't afford to ignore warnings of a dry summer to come. However, dry summers should not be a cause for worry, since they are a normal part of our weather pattern. What is a cause for worry is a slavish adherence to garden techniques that are not appropriate in dry-summer areas. High on the list of such techniques is that of overwatering.

Long an indulgence that went unchecked, overwatering is about to become a major community issue. The biggest problem is that many of the worst water wasters are unaware of doing anything wrong. Indeed, water district studies show that most high users feel proud of what they perceive to be appropriate conservation measures, even when they are in fact grossly misusing this precious resource.

How can such a disconnect come about? In large part, the problem lies with irrigation systems that are set (often by professionals) to run too often and too long. Any system that results in soggy lawns, beds and borders, even temporarily, is delivering too much water.

What's enough? In the Northwest, lawns need about an inch of water per week during the hot months. Most border plants do fine on that much or less. However, many if not most irrigation systems are delivering as much as 10 times this amount.

If there was water to spare, this would still be a problem, since overwatering is a leading cause of fungal disorders and root rots in lawns and border plants. Overly wet soils also host more crane fly larvae and encourage rampant weeds like horsetail and buttercup.

Gardeners in the Northwest succeed brilliantly when they understand local conditions and work with them. Since dry summers are part of local conditions, it's high time our gardens reflected that fact. In recent columns, we've looked at several aspects of what is called dry gardening, a method that uses a minimum of water to get a highly attractive and even lush result.

The look of a dry garden may or may not be very different from the look of a waterhog garden. The main difference is in the roots of the plants. Drought-tolerant plants tend to have extensive root systems that take advantage of all available soil moisture.

In waterhog gardens, even nominally drought-tolerant plants tend to be shallow-rooted for two reasons. First, they don't need to range very far to find water. Second, sodden soil tends to be sour and inhospitable to a wide range of garden plants. In sodden soil, roots stay shallow in order to get enough oxygen to survive.

One key to success in dry gardens is to select a combination of drought-tolerant and site-adaptive plants that thrive on benign neglect. This doesn't mean that we abandon them to their fate (which would generally be fatal). It does mean that we choose plants with an eye to their survival abilities as well as beauty and productivity.

In the early stages, dry gardening is not about benign neglect. It's about giving these carefully chosen plants a good start. It's also about making sure they get through the vulnerable first year or two by providing moisture as needed.

Mulching appropriately helps us do both very effectively. In my gardens, 4 to 6 inches of compost and mulch are spread every year. This conserves soil moisture and keeps weeds down at the same time. This year, I'm trying a new mulch from Cedar Grove called Booster Blend that combines mature compost with washed dairy manure.

This makes excellent sense, since it combines two of the most valuable soil improving materials known to soil scientists. Composted, washed dairy manure has few if any weed seeds and is a splendid soil tilth builder. Compost is also an invaluable soil food, promoting the rapid expansion of colonies of beneficial soil biota. Mixed with compost, dairy manure is a very fine amendment for both heavy and sandy soils and also works extremely well as a top dressing.

To give your young plants a great start, prep your beds generously with mature compost before planting. At planting time, combine compost and/or dairy manure with the loose soil in the planting hole and blend more compost with the backfill soil as well. After planting, top dress with more compost and/or washed dairy manure, extending the mulch to the projected dripline of the plant.

In most situations, it will be most effective to mulch an entire bed or border rather than spot mulch. However, when planting trees or shrubs in new areas, it works fine to amend as you go. Just be generous in your prep, making each hole 3-5 times wider than you think it should be.

Don't make the hole extra deep, though, and be sure that the soil below your new plant is firmly packed, without pockets of soft materials like compost. Even though plant roots need air, large air pockets can kill baby roots, while soft material like compost and manure can create ideal conditions for root rots.

You do want to use plenty of compost at the sides of your plants, in order to encourage a wide-ranging root system that will quickly become self-supporting. A blanket of mulch will help lock in soil moisture while still allowing good oxygen flow to the growing roots.

Contact Cedar Grove: 877-764-5748.

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Ann Lovejoy can be reached via mail at: 8959 Battlepoint Drive N.E., Bainbridge Island, WA 98110. Her latest book is "Ann Lovejoy's New Fresh From the Garden Cookbook: Recipes Inspired by Kitchen Gardens" (Sasquatch, 208 pages, $22.95).

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