Rain. During an entire year, a meager three-hundredths of an inch falls on Arica, Chile, while halfway across the Pacific, in the Hawaiian Archipelago, Mount Waialeale receives a sopping 460 inches.
Much of the eastern United States provides a congenial climate for many garden plants during the growing season, averaging 4 inches of rainfall a month throughout the year. That would seem to complement nicely the inch of water per week recommended for most garden plants. Four inches of rainfall a month is more than enough water to supply the 33 gallons used by a tomato plant, the 54 gallons needed by a corn plant, even the 1,800 gallons quaffed by a single large apple tree.
So much for theory.
Problem is, whether you’re in the humid Northeast or the drier West, rain does not always fall in the right place at the right time from a plant’s point of view.
Four inches of rain dumped from the sky on the Fourth of July, with none again until the first of August, would meet July’s quota. But much of it might run off the surface of the soil or down through the soil beyond the reach of roots. Plants could be thirsty again by the middle of July.
One way to remedy this feast-or-famine situation is to help all water falling from the sky get into the soil. Small catchbasins built up around individual trees and shrubs keep rainfall in place, containing the water long enough for it to slowly seep into the ground. Organic mulches such as straw, compost, wood chips and leaves prevent raindrops from pounding then sealing the soil surface, and thus help water percolate into the soil.
Once water is in the ground, those organic materials also help hold it there. As mulches, they help by preventing evaporation from the soil surface. Mixed into the soil, these organic materials act like a sponge to cling to water for later use by plants.
Once you have gotten water into the soil and held there, why waste it on weeds? A full-grown ragweed plant sucks about 2 gallons of water per day from the soil, water that could be plumping up juicy, red tomatoes. Timely weeding keeps water in the soil for the plants we choose to cultivate.
Yet for all your water conservation efforts, sometimes you just gotta water your plants. Choose from one of two approaches: Water either deeply and infrequently with a sprinkler or bucket; or water lightly and frequently with so-called “drip irrigation.”
Either way, the average amount of water needed translates to that same 1 inch (about a half-gallon per square foot) applied once each week with a sprinkler or bucket, or 1/7th of an inch applied every day or spread throughout each day with drip irrigation. Drip irrigation is easily automated with the use of a battery-powered timer at the spigot.
When your time or energy is running short — often the case when hand watering and using sprinklers — you might want to do triage: First, care for those plants that need water the most. The first plants to suffer from thirst are annual flowers, and leafy vegetables such as lettuce, spinach, and cabbage, as well as any perennials or trees you set out just this spring.
Roots of full-grown trees and shrubs run deep into the soil, so these plants can wait longest for water. Roots of perennial flowers, and vegetables like asparagus, beans, peas, cucumbers, melons and tomatoes, also can tap moisture a few feet down in the soil.
Lawns tolerate drought by going semi-dormant and tawny, then perk up when moist conditions return.
Writing about a lack of water is like doing a rain dance. As you read this, your garden plants may have just drunk in a deep, summer shower.