In an ideal world, every garden would receive a consistent one to two inches of rainfall per week. This can happen for a few weeks or even months, but rarely does a summer go by without a dry spell.
Plants need water to transport nutrients from their roots throughout the plant, and to perform photosynthesis, which, with the help of light, transforms water and carbon dioxide into sugar and oxygen.
Drought can lead to smaller or tough fruit and vegetables, or none produced all. Some plants may bolt, going to flower prematurely and stopping growth to put the focus on seeds for the survival of the species.
The one-inch-per-week minimum is more water than you may imagine; for a garden that is 10 feet by 10 feet, that’s 62 gallons. Get a quality hose—it’s about to become your new best friend—and buy or make a rain gauge, because overwatering presents its own set of problems.
Exceptions to the Rule
When it comes to watering, there is no one-size-fits-all rule. The question of just how much to water depends upon the plant species. For example, onions are happiest with regular watering, while tomatoes and squash like things a little bit drier and are actually prone to disease if overwatered. Research each plant’s individual requirements, and group those with like needs together to make things easier. Always remember that the one-inch-per-week guideline is a combination of rain and your watering, and you may need to double that amount in the peak of summer.Another key factor is the soil. Water flows freely through sandy soil—often too freely. If you haven’t planted the garden yet, amend it with compost for better water retention. Even with the addition of compost, sandy soil usually requires more water than clay soil, which holds moisture very well and can quickly lead to overwatering and the decline of your plants due to their roots being too wet. Adding compost will break up the hard clay and increase permeability.
To mulch or not to mulch is another consideration, to which the answer almost always is yes. Mulching is the No. 1 water-conserving technique, according to the Farmer’s Almanac. It reduces evaporative moisture loss and keeps the soil cooler. Note that mulch should go on top of the soil, not be mixed in.
The When
When the top of the soil looks dry, there’s a temptation to reach for the hose. Instead, take out a trowel; if the soil two inches below the surface is dry, it’s time to water. Regular, shallow watering to keep the soil damp encourages shallow roots. Deep, less-frequent watering encourages deep roots that will reach into the soil seeking residual water. Soak the soil to a depth of five to six inches.The Where and How
Watering at the base of a plant gets the water where it’s needed: the roots. This has the added benefit of both conserving water and keeping the foliage dry, which reduces leaf diseases such as powdery mildew. Watering outside the root zone encourages the germination and growth of weeds. Low (so as not to wash away soil from the plant roots) and slow watering allows the water to soak down into the soil, avoiding puddling and run off.Sandy soils will absorb water faster than heavier soils. When in doubt, or when watering garden plants that have gotten dried out, water thoroughly, then repeat after 15 to 30 minutes, for deeper saturation. This can be accomplished by patient hand watering with a watering can or hose, or drip, trickle, or soaker systems. Some sophisticated irrigation systems are designed to turn on based on the weather or soil moisture.
Broadcast and lawn sprinklers may look like they simulate rainfall, but they are highly inefficient. Wind can blow the water into areas you don’t want it and away from where you do. Heat can evaporate it before it reaches the soil. Plus, they wet plant leaves, leaving them vulnerable to mold, mildew, and disease. In some cases, the plant foliage may be so thick that the water doesn’t reach the ground at all.
