GARDENING : Water: Giver and Taker of Life

Watering probably tops the list of cultural practices harmful to plants, particularly new ones. However, a few basics smooth the problems. The main goal should be to keep plants from the stress stage.

Longtime gardeners constantly look at a plant for signs of stress and what may be causing it. Being a good observer requires monitoring not only the plants but also soil and weather conditions.

It also will help to group plants according to water requirements. Place together trees, shrubs and flowers that have high or low requirements, which helps to keep them from being over- or under-watered. While not always possible, such grouping should be a leading objective.

There also is a need to understand why watering requirements change as plants grow, and to water accordingly.

Signs of wilting are bad news. Oddly, it can be caused by too much water or too little.

Established plants can tolerate some wilting and probably won’t die from lack of water; they just won’t grow very fast or look as good.

Conversely, new plants and seedlings need watering before they reach the stress stage. They become established through root growth and a good top-to-root balance. Some species take one to two years, or even more. Until you are sure they are established, give them close attention. Don’t try to water on a fixed schedule.

With a newly purchased plant, the original advice is usually to water every couple of days after planting. The plant may look happy for months. But if such watering continues, it begins to wilt and drop leaves despite the attention lavished upon it. Actually it is drowning from lack of soil oxygen. More water finishes it.

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A better starting point usually is to water every other day for the first couple of weeks and then reduce this to once or twice a week.

Light but daily watering tends to establish shallow root systems subject to quick drying. Because a plant wilts if the roots don’t have sufficient moisture, the deeper the roots go, the less vulnerable the plant is to fluctuations at the soil surface and sudden drying. Deep watering is good insurance. This means applying the water slowly so that it soaks in instead of running off.

Conditions vary, of course, but start by assuming that one to two hours of slow soaking will wet the average soil to a depth of two feet and six to eight hours will reach four to five feet. In general, flowers root at least one-foot deep, established shrubs three to four feet deep and most mature trees as much as five feet or more. Determine the moisture depth by how easily a long screwdriver or narrow rod goes into the ground. It is hard to push into dry soil.

Deep watering also flushes soil salts from the root zone, which is particularly good insurance in arid regions.

Mulching is another good technique. Apply organic material to the soil surface to prevent drying, hold down weeds and keep temperatures cooler.

The most convenient and time-saving method of watering a landscape is likely to be an automatic irrigation system, eliminating the need to drag hoses to various locations.

Most gardeners find the convenience is worth the installation cost. But observe the system frequently while it is running to catch problems before they become serious.

Another point to remember: Roots don’t seek water, they follow it. So they are reluctant to grow into dry soil.

Many flowers are low-water users. Where possible, it makes sense to opt for those that don’t require regular watering.