Apply enough water to wet the entire root zone and to encourage deep rooting. Deeper roots are better able to withstand periods of drought; shallow watering, on the other hand, leads to shallow roots and plants that are susceptible to drought and strongly affected by fluctuating temperatures. (Properly irrigated, roots of lawn grasses grow about 6 inches deep, shrub roots about 12 to 18 inches deep. Most tree feeder roots, even of large trees, are within the top 2 feet of soil; they extend well beyond the tree's drip line.) How can you tell how deep water is penetrating? Push a stiff metal rod into the soil after watering. It will move easily through wet soil and will stop or become harder to push when it hits dry soil.
In heavy clay soils, you may have to pulse-irrigate ― watering until puddling occurs, stopping until the water is absorbed into the soil, then repeating ― to avoid wasteful runoff. Automatic controllers make this easy.
Apply water with care
Irrigate early in the morning, when winds are calm and evaporation is at a minimum, so that water goes into the soil and to plant roots.
Water only the target area. There's no need to sprinkle sidewalks, driveways, or the side of the house.
Apply a layer of mulch (such as ground bark or gravel) to the soil to reduce evaporation. Use a 1- to 2-inch-thick layer around annuals, perennials, and vegetables and a 3-inch-thick layer around trees and shrubs.
Maintain your irrigation system
To make sure your system operates efficiently, examine it frequently, checking for leaks, clogs, or misdirected sprinklers or drip-emitters.
Sprinklers. Look for signs of trouble. If sprinklers are spraying more water on paving or other unintended areas than on lawns, adjust them. Unclog heads, using a knife or a piece of wire. Water-filled valve boxes or leaking sprinklers may be a sign that valves need to be repaired or replaced.
Drip-irrigation system. Check for leaks ― geysers, puddles, eroded soil. Secure tubing that has come loose. Replace or clean clogged drip-emitters and mini-sprinklers. Clean the filter as needed.
Adjust watering schedules with weather
Since plants use more water during hot, dry weather, you need to water more often in summer (and on windy days) than in spring or fall. In many regions, plants don't need any supplemental water in winter.
A hose is enough to handle your watering if you have just a few outdoor plants or even a small lawn.
Hoses vary in quality. Depending on the manufacturer, they may be made of rubber, vinyl, or a combination. The best hoses incorporate multiple layers of reinforcing fabrics such as nylon or rayon, and they have strong couplings made of brass (the thicker the better) and quality swivels (hexagonal-shaped for easy gripping). Also look for a protective collar just below the coupling, which prevents the hose from kinking at the faucet.
Garden hoses vary in length (25, 50, 75, and 100 feet) and inside diameter (1/2, 5/8, and 3/4 inch). The larger the hose, the greater the volume it delivers. To tailor your hose to various water situations, you can choose from these attachments.
HOSE-END NOZZLES turn hose-flow into a variety of sprays, from strong jet to gentle mist. Some have long handles, making them especially helpful for watering hanging baskets. Many have built-in shut-off valves.
PORTABLE SPRINKLERS (impulse, oscillating, rotating, stationary, or traveling) help you water small lawns. Choose a sprinkler with a pattern that matches the shape of the lawn you need to irrigate.
DEEP-ROOT IRRIGATORS attached to hoses can inject water 18 inches down into tree root zones.
ON-OFF TIMERS, at their simplest, are designed to fit between a faucet and a hose. You set a dial and the timer turns off the water at the designated time. You can also use an egg timer to remind you to turn off the water.
HOSE Ys turn one faucet into two or more. On some models, each branch of the Y has a shutoff valve, so you can use them separately; this is handy if you are running several drip-irrigation lines or soaker hoses from one faucet.