SOAKING IT ALL IN
The number one No. 1 cause of plant death may might surprise you. It’s not pests, diseases or lack of fertilization, but under- or over-watering. And the hot, dry days of August and September are probably the most challenging months to properly water your plants.
“Like people, plants are under more stress during the heat of summertime,” says Steve Hollister, manager of Armstrong Garden Center in Santa Ana. “When it’s hot, plants need more water, but not too much. Watering can be a delicate balancing act.”
Don’t water enough, and your plants die of dehydration. Water too much, and root rot can set in.
Learn to water plants properly, though, and you’ll be rewarded with a lush, healthy landscape. Proper watering generally also means using much less water.
The secret is to water according to plant needs, not your timetable, Hollister says. “Don’t set a watering schedulefor your plants to follow, because they don’t listen.”
How damp or dry the soil is varies from day to day and season to season, so you can’t base watering decisions on when you last watered. The condition of the soil’s surface is also not a good indicator, because it can look dry, but the soil directly underneath may be very wet.
Although you can sometimes tell a plant needs watering if it is wilting, that’s not always an accurate sign. A waterlogged plant suffering from root rot also wilts.
The only precise indicator of when to water is the moisture level of the soil.
“Do some inspecting,” Hollister says. “Stick your finger into the soil about 2 inches, or open up the earth with a hand trowel and feel. If the soil is moist, the plant doesn’t need water.”
An inexpensive, easy-to-use tool for determining what’s going on below the soil’s surface is a moisture meter. This is a metal rod you stick into the soil, and it tells you if the soil is dry, damp or wet. It can be used on most plants, except for deep-rooted plants like large trees.
Learning to water properly also means understanding how to water your particular soil type.
Clay soil is heavy and resists water penetration, so it must be watered slowly and deeply. The worst thing you can do to clay is what many sprinkler systems are set up to do, and that is water rapidly.
“Because clay soil is slow at accepting water, when you water quickly, the water doesn’t have enough time to penetrate the ground and it just runs off and is wasted, or there is very uneven absorption of water. It can puddle and soak some areas and leave other areas dry,” says Gary Matsuoka, president of Laguna Hills Nursery in Lake Forest.
Another side-effect of quickly watering clay soil is shallow root formation, which leads to weak plants. You will also end up with salt accumulation, which burns plant roots and can lead to above-ground leaf burn.
Sandy soil has its own problems. Although it absorbs water quickly, it washes through just as fast, which makes it important to water this soil type slowly and thoroughly. One main difference is that sandy soil must be watered much more frequently than clay.
How you water also depends on the type of plants. Lawns need to be watered much differently than trees and shrubbery, and annuals, perennials and potted plants have their special water requirements.
Armstrong Garden Center, (714) 542-4145. Laguna Hills Nursery, (949) 830-5653.
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Lawns
Although many people water their lawns every day, rarely does a lawn need watering more than three times a week, Hollister says. “Some hardy grasses like hybrid Bermuda and turf-type fescues can go a week without watering,” he says.
If your sprinkler system is set to water your lawn daily or every other day for a short duration, nurseryman Gary Matsuoka suggests gradually switching to the following watering plan, which was developed by UC Riverside staff:
Set your sprinklers to run for five minutes three times, waiting an hour between each application. “This will water the grass more evenly, prevent runoff and use less water,” he says.
Watering your grass in this manner needs to be done only three times a week in hot weather and twice during cool times of the year.
Keep in mind these are approximations. The best way to know how much water your grass needs is to check its moisture level.
Also audit your sprinkler system periodically to ensure even water distribution. Place a number of short, straight-sided cans around your lawn, run the sprinkler for five minutes and then stop and compare water level in the cans. If one can has significantly different level, adjust the sprinkler.
Trees and Shrubs
As a rule, the larger the plant, the less frequent the watering. Big, well-established trees might need watering only once every month or two during the dry season, and the same might apply to large shrubs. Some trees and shrubs are drought-resistant, once established, and will survive on rainwater. Research each tree and shrub to determine its watering requirements.
Many experts feel sprinkler systems are not a good choice for watering trees and shrubs because they spray, rather than slowly distribute, water. Water manually by leaving a hose on low for several hours. Or if the system is automated, use drip irrigation, which enables you to tailor how much water each individual plant needs.
Matsuoka, however, has a different opinion on watering trees and shrubs. He thinks drip irrigation systems are good when trees and shrubs are young, but he feels sprinklers are better to use after plants are established.
Annuals and Perennials
More shallow-rooted plants such as seasonal flowers and small perennials can require water several times a week, depending on the weather and the type of plant. Because they can dry out quickly, it’s best to check the soil moisture level at least every two days in hot weather. Water thoroughly when the soil approaches dryness.
Sprinklers can be used to water annuals and perennials, but soaker hoses or drip irrigation are also effective, especially if you are growing flowers such as zinnias and snapdragons, which are susceptible to mold and rust that is caused by wet foliage.
Container Plants
Potted plants are completely dependent on you for water. In very hot weather, container plants can require watering as much as once a day, depending on the plant, its location and the size and type of pot. Nonporous pots such as plastic or glazed containers tend to dry out much less quickly than clay and wood.
Before watering, check potted plants with a moisture meter or your finger, or pick up small plants and water when they’ve become lightweight. It’s important to water containerized plants thoroughly. Don’t stop until water runs out of the drainage holes.
