IN THE GARDEN KEEP SPRINKLERS IN TUNE WITH YARD.

Byline: JOSHUA SISKIN

Hot weather is already here, and you can sense the fear and trembling in gardeners' hearts. You cannot rely on rain anymore to get everything soaked, nor on cool weather to keep the soil from drying out.

Yes, it is time to turn the sprinklers back on. Sprinklers are the ultimate con artists. You have sprinklers all over your lawn and flower beds, see clouds of mist every morning when the water comes on, and confirm that every square inch of your landscape and garden is getting irrigated. Yet still you have dry spots in the lawn and some of your annual flowers are shriveled.

Never rely on sprinklers. You need to personally inspect your lawn and beds frequently to make sure everything is growing the way it should.

Assuming that your sun plants are getting enough sun (but not too much) and that your shade plants are getting enough shade (but not too much), 99 percent of your garden problems are going to be water-related. Where not enough water is available, green grass turns blue and then brown, and growth of flowers and perennials is spindly or wilted. Where too much water is present, insect pests and fungus diseases proliferate.

Let us assume that every inch of your lawn and garden is, in fact, getting sprinkler coverage. Now let us see why you are still having problems.

1. Water coverage is provided by a single sprinkler only. Each spot on your lawn or in your beds should be covered by at least two or ideally three sprinklers. The reason for this is that water is not delivered evenly within the area that a sprinkler waters. For instance, the area closest to a sprinkler gets the least amount of water from that sprinkler, which is why landscapers talk about ``head to head coverage.'' If your sprinkler heads are 10 feet apart, they should each water to a distance of 10 or ideally 12 feet to ensure overlap.

2. Sprinklers are too short. There are 3-inch, 4-inch, 6-inch, and 12-inch pop-up sprinklers. Some people make the mistake of using 3-inch pop-ups in their lawns. If your sprinklers pop up less than 4 inches, your grass will never be properly irrigated; your sprinkler spray will be blocked by the blades of grass around the sprinkler. Do not use pop-up brass sprinklers on lawns, since they are always too short. In shrub and flower beds, 6-inch pop-ups are the standard size used. This is also a mistake. Twelve-inch pop-ups do a much better job of watering everything from ground covers to annual flowers, perennials and woody shrubs.

3. Sprinklers are not uniform. All sprinklers in a circuit must be the same kind. Do not mix Toros and Rainbirds; do not mix spray heads with rotary heads. Uneven water distribution will be the result.

4. Lawns and planter beds are on the same circuit. Grass requires two to four times as much water as planter beds, depending on what is in the planters. You will invariably overwater your planter beds if they are irrigated on the same line or circuit as your lawn. Have separate circuits with separate valves for lawns and beds.

5. A plant is blocking the spray of the sprinkler. Not only tree trunks get in the way of sprinkler spray; small stems and even leaves of ground cover can do the trick. You must observe your sprinklers while they are on to detect what is blocking the spray.

6. The soil is compacted or drains too quickly. A lawn that is not regularly aerated and/or dethatched eventually resists water penetration due to compaction or thatch accumulation. By contrast, a soil that is too sandy, or too full of desiccating amendments such as peat moss and perlite, will drain so quickly that even watering twice a day during the summer will not be enough to keep plants from wilting.

7. Soil drains poorly or water accumulates in discrete areas. Where soil drainage is poor throughout an area, you will have to alter your plant selection to include species, such as Mexican heather (Cuphea hyssopifolia) and Coreopsis, that are impervious to bad drainage.