With summer heat baking much of the nation, it’s a good time to review some of the basics of watering. Our horticultural advisors have lately received a number of contacts about issues pertaining to plants that are being either under-watered or over-watered.
Cathy Hughes, Senior Horticulturist for the Customer Service Call Center, says, “I just had a phone call that perfectly illustrates the concern. The customer lives in Queens, N.Y., and she wanted to know why the leaves on her ‘Patriot’ hostas turn brown every summer. I asked how long they’ve been established, and how often they get watered. She said they were planted three years ago, and are watered with an automatic sprinkler system every morning and evening for 15 minutes each time.”
Automatic sprinkler or irrigation systems are a convenience for many gardeners, but they need to be properly programmed and adjusted for weather conditions. We’ve all seen sprinkler systems running after (and even during) a deluge. Auto irrigation systems also are generally the culprit when watering is being done in 15-minute intervals.
A better method is to water plants less frequently but more deeply. You want the soil to dry out between waterings because that’s what encourages healthy root systems. “Shallow watering, the kind you get when you turn on the hose or irrigation system for 15 minutes, promotes shallow root systems because plants don’t have to go looking for water,” Cathy says. “The water problem is exacerbated if the soil is mulched because the mulch facilitates water retention.”
As a general rule of thumb for established perennials, Cathy advises “watering when the soil is dry to a depth of 2”, and always checking the soil before watering because hot weather does not necessarily mean the soil is drying out, especially if conditions are humid.” In addition, plants may wilt as a response to high temperatures, but the soil may still be moist. If the plant recovers either late in the day or early in the morning, and you have not watered, this is a clear indication that the soil is still moist.
The best way to check the soil is to stick your finger in the dirt, or push a spade in and remove a clot of earth to see how deep the dryness goes.
Gardeners should keep in mind that different plants have different watering needs. Annuals, which are planted in spring and give their all in one season, generally need more water than perennials that have many seasons to develop root systems; plants situated in full sun almost always need more water than those in shade; plants that live beneath large trees, where they’re forced to compete against tree roots for water, will need more hydration support than most; and new plantings will require more regular watering than established plants.
Container pots are a different story. They tend to dry out quickly, especially if pots are made of porous materials such as terra cotta. Most pots, unless they’re filled with succulents and other drought-tolerant plants, will need to be checked daily especially in the heat of summer.
For tips on proper watering of your vegetable garden, see our June 14, 2016 blog post “Caring for Your Vegetable Plants.”