How serious do we really need to be about watering our gardens and landscapes? Quite serious. Like us, plants depend on water for their survival. They may scrape by with less-than-ideal amounts of moisture, but to thrive and look their best, most need a regular supply throughout the growing season. Here's why:
• Water is a component of all plant cells and forms the transport system within a plant.
• Water keeps plant stems stiff and leaves expanded so they can intercept the sunlight needed for photosynthesis.
• Mineral nutrients in the soil must be carried by water into the roots, then distributed throughout the plant.
• Water drawn in by roots travels up stems, then evaporates from leaves, cooling and protecting plants from overheating.
It's easy to tell when flowers and vegetables -- or houseplants, for that matter -- have gone too long without water. Flowers wilt and foliage becomes flaccid. Sometimes the stems flop down, too. Amazingly, they often pop back up within hours after water is restored to the root zone. But don't expect them to do this trick too often.
Lack of moisture also causes grass to wilt and lose its ability to spring back when you walk on it. If grass dries out because of water deprivation, it will go into dormancy, turning crisp and tan -- only to send up new green growth when regular moisture levels are restored. (At least most common Kentucky bluegrasses can be expected to green up again. We learned in the drought of 1988 that some of the more luxuriant, "improved" bluegrass lawns died after several weeks.)
Young trees are particularly vulnerable when water is in short supply. Their leaves droop or develop brown or rusty discoloration called "scorch" along their margins. Evergreens suffer, too, although the signs are less obvious. Symptoms may not show up until the following spring, when evergreens exhibit "winter burn" -- brown, dead needles -- particularly on portions that were exposed to lots of drying sun or wind.
The better established your plants, the more resilient they will be in response to hot, dry weather. So give young plants even more tender loving care. This includes most flowering annuals and garden vegetables except rhubarb, a perennial. And it certainly includes newly seeded or sodded lawns as well as trees and shrubs that were planted in the past few years. Flowering perennials are usually pretty well-established after a couple of years in the garden.
It always makes sense to use water wisely. For efficient watering, do it early in the day when temperatures are cooler and there's less wind. Plants won't be harmed by afternoon watering, but much of the moisture will evaporate before it hits the ground. Also avoid evening sprinkling, unless it's your only option. Plants dry very slowly at night, increasing the likelihood of disease.
Hand watering with a hose is fine for containers but rarely delivers enough moisture to thoroughly soak the roots of garden and landscape plants. Instead, use soaker hoses or sprinklers that may be left in one place long enough to wet the soil 5 or 6 inches down.
PLANTS LOVE MULCH
Mulch helps conserve moisture by keeping soil cooler and cutting down on surface evaporation. Use a couple of inches of dried grass clippings, chipped leaves, straw or partially finished compost in flower or vegetable gardens. Cocoa bean hulls, pine needles, shredded bark and wood chips look nice around flowering perennials. Spread bark or wood chips 3 to 4 inches deep around young trees and shrubs. Just be sure to leave a little air space around the trunks or stems before mulching.
If you want a weed barrier under the mulch, use landscape fabric, not solid plastic. Both water and air can pass through easily, keeping plant roots healthy.
Deb Brown is a horticulturist with the University of Minnesota Extension Service Yard and Garden Line. For help with garden, plant and insect questions, call the Extension Service at 612-624-4771.