Understanding Drought Stress
Frederick County Master Gardener Program
Prolonged drought stress to plants is unhealthy and predisposes them to pest problems. A plant under drought stress is in a weakened state and its defenses are low.
Insects and diseases take advantage of the situation and add to the plants' stress. The result is often observed the following season with pest damage that seemed to appear overnight. When in reality the problem started the previous season during or following the drought.
The solution is to avoid prolonged drought conditions through proper watering.
Identifying drought conditions is not always easy. Outward signs on deep rooted plants typically are not obvious. Many variables play a part in reaching drought conditions, these include lack of natural rainfall; soil type; air
temperature & humidity; wind conditions; sun exposure; and also plant type (root depth). Deep rooted trees can obtain water longer during drought conditions than shallower rooted shrubs and flowers. To simplify things remember that lawns require the most water in a
landscape. Annual and perennial flowers planted in full sun are next, shrubs follow, and trees are the least needy. There are plants in each category that are known to be very drought tolerant. A list of these plants is available from the Cooperative Extension office (call
the number below).
When temperatures soar and natural rainfall diminishes begin to observe your landscape often or daily for signs of drought stress. Find a plant to use as an indicator. Lawn areas in the sun next to walks and driveways show signs of heat
stress early. Lawns require about an inch of rainfall (or irrigation water) per week to avoid drought stress. Certain annual flowers planted in full sun (impatients, begonias) are also good indicators of drought. Indicator plants and recently installed plants require water
more frequently than the rest of the landscape. I often observe leaf wilting on trees and shrubs that were planted in the spring when the first hot spell of summer hits. When the indicator plants show signs of drought apply water to relieve them and pay attention to the
results. Plan on watering the entire landscape within a day or two. Although the current water restrictions are keeping most of us from watering our lawns and gardens, the following tips will help conserve water as you irrigate to avoid drought stress:
Mow lawns higher during the hot summer months, a height of 3 - 31/2" is best.
Control weeds, they compete with the desirable plants for water.
Maintain 2 - 3" of mulch in flower beds to reduce evaporation; cool soil; and control weeds.
Water infrequently, slowly and deeper. Frequent light watering encourages shallow root growth and weeds. Water for a longer duration less often.
Water in the morning, complete watering cycle before 11:00 a.m. for best results. As much as 40% of the irrigation water can be lost to evaporation during the heat of the day. If you must water at night begin after 8:00 p.m.. Remember
that watering in the late day and night promotes fungal diseases.
Direct water to the plants. Avoid over-spraying sidewalks, driveways and streets because that wastes water.
Repair leaks. Leaking hoses and irrigation pipes also waste water by not applying it to the needed area.
Use soaker hoses or drip irrigation. These products apply water to the soil surface only and can reduce water use by 65-70%.
Collect rainwater. Collecting rainwater is a great way to take advantage of the late day thunderstorms that occur. Often water from these storm events run off before doing much good for the plants. By collecting it in a rain barrel and
applying it to an area slower it will seep into the root zone and benefit the plants. This practice is allowed under the drought restrictions as well.
Through identifying drought stress and observing the results of watering you will get a " feel " for the particular needs of your landscape. The constant observation can also alert you to developing pest problems before they become very
damaging. When the high temperatures (above 90F) and lack of rainfall persist for more than a week, you will see drought stress if you look for it.
Read other articles on gardening in drought conditions
Read other articles written by Robert Bishop