February 2018

Purdue launches Website to help Indiana gardeners deal with drought

Rosie Lerner, Purdue Extension Consumer Horticulturist. Photo courtesy Purdue University.

As if home gardeners don’t have their hands full just trying to keep their plants healthy in this drought and scorching heat, they also need to know this: environmental stress this year could influence how the plants develop next year, says Rosie Lerner, Purdue Extension consumer horticulturist.

Gardeners ultimately may have to decide which plants to try to save and which to let go. (The Hoosier Gardener offers some suggestions on setting watering priorities.)

“Gardeners have a battle on their hands to keep plants healthy when extremely high temperatures are accompanied by lack of rain,” Lerner writes in her June column titled “In Times of Drought” and discusses in the video of the same name. Purdue also has launched a Website to help Indiana gardeners deal with the drought.

“Keep in mind that next year’s growth will be determined by buds that form this summer and early fall. Flower buds for spring flowering and fruiting plants will also be developing during this time. So the damaged inflicted by drought now may affect next season.”

Sandy soil and containerized plants will need more frequent irrigation than a heavier clay soil or a loam that has good organic matter content.

Leaf scorch on trees and shrubs, appearing as a browning along the edges of the leaves, is very common in dry summers. While minor cases of leaf scorch are not very harmful, prolonged lack of moisture can spell disaster for landscape plants. “Young and newly established plants are most susceptible to the dry conditions, but even established plants may reach a critical point during prolonged drought. Branch dieback, combined with eventual root death, will make plants more susceptible to winter injury. Plants that were already under stress from other factors may succumb to severely dry soils,” Lerner says.

Direct watering of landscape and fruit plants to where the roots naturally occur. While woody plants do have some roots that grow very deep, the feeder roots, which are responsible for most-efficient water uptake, occur in the top 12-18 inches of soil. They are concentrated below the drip line of the plant and beyond, rather than up close to the trunk. Apply water at a slow enough rate to allow penetration, rather than wasting water by runoff, and thoroughly soak the target area. Don’t apply the water any faster than one inch per hour. As with annual plants, mulch will help prevent moisture loss due to evaporation.

While many homeowners regularly water their lawns to keep them green throughout the summer, others prefer to allow the cool-season bluegrass to become dormant in the summer by withholding irrigation. In “normal” years, this strategy works just fine. Dormant bluegrass plants can generally last about four to six weeks without water.
But during severe drought, dormant lawns may begin to die if some water is not applied. To avoid grass plant death while minimizing water usage, apply one-half inch of water every two to four weeks. The grass will not green up, but the crowns will stay alive.Green up will occur with the return of natural precipitation and more favorable temperatures. Check out more info on managing lawns during drought.

Compounding the problem are any watering restrictions or a gardener’s limited ability to water larger numbers of plants.

The ideal time to water is during the early morning hours ending by 8 a.m. This makes maximum use of water while allowing foliage to dry. Watering during midday, when temperatures are high, sunshine is strong and winds are brisk, wastes substantial water. Watering in the evening is convenient for many and watering at night may coincide with lower water-use demand; however, it can make plants more susceptible to disease infection by providing the moisture needed by fungi and bacteria. Of course, many communities impose restrictions on water use during times of drought, so ideal practices may not be possible. If your community is under restricted water use, it is certainly better to water when permitted than not water at all.

“You may have to limit watering and prioritize which plants will be rescued — a bit of garden triage, so to speak,” Lerner says.

Among her tips:

  • New plants need 1 to 1 1/2 inches of water per week to maintain optimum flowers foliage, roots and fruits. In times of drought, established plants may tolerate 10 to 14 days between watering, but be aware that problems such as fruit cracking and blossom end-rot will increase, Lerner says
  • The best way to water a garden is by soaking the soil thoroughly — but slowly — in one application. “This slow, deep watering will encourage deeper root growth, which in turn will be better able to withstand drought,” she says. “Frequent shallow water encourages shallow roots, which are more likely to succumb to heat and drying of the topsoil.”
  • Household “gray water” — such as that leftover from a bath or washing dishes — can be used but with caution. “Gray water could have a high level of detergent salts, which can eventually build up to harmful levels in the soil” Lerner says.

Water from a water softener has a high level of sodium that can tighten soil, preventing water from passing through it. “Use gray water only as a last resort, and use it as sparingly as possible to avoid salt buildup.” she says.

Lerner says gray water should never be used to irrigate edible crops or on plants in containers because of health risks associated with it.

By Rosie Lerner, Purdue University Consumer Horticulturist

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