University of Manitoba - Faculty of Agricultural & Food Sciences - Drought

Problem type: Environmental

Name of problem: 

Plant name(s): 
All plants

Symptoms / Characteristics:
Herbaceous plants (annual and perennial plants lacking woody stems) are the easiest group of plants to recognize when deprived of water. Foliage will begin to wilt and droop as soon as the roots have reduced water uptake. Annuals are not as deeply rooted as perennials therefore show signs of drought much more readily. Drought symptoms on woody plants are much more difficult to recognize and signs of drought will usually not show for up to a year later, when the plant is already in poor health.

Leaves on deciduous trees may show marginal browning and scorching. When the margins of leaves show discoloration and seem in poor health, it generally shows that there is poor transport of water or nutrients or a lack of water and nutrients reaching the leaves. Drought may be one reason why this can happen, but there are many other factors that can block the transport of material inside a plant, such as insect activity, diseases, root damage or mechanical injury to the plant. Leaves on trees may turn yellow or red and can drop prematurely in response to drought. To check if a plant is still living, an easy test is to simply peel back bark on a twig or branch and see if there is green tissue beneath the bark. If the inside appears brown and the branch is brittle, that branch is dead. Twigs and branches can dieback and even larger limbs can die or break off during windy conditions.

Coniferous plants are even harder to recognize when stressed by drought. They can remain green for up to several weeks after the plant had died leaving no hope for recovery. Early season drought will cause new evergreen shoots to droop or curl as their sign of wilting. Spruces and pine trees are easiest to detect when this occurs. Symptoms of late season drought on evergreens may not be evident until the following year. Winter browning damage on evergreen trees and shrubs generally occurs in late fall but does not show symptoms until the following spring.

Some trees under drought stress will produce epicormic shoots and/or suckers on the trunk or upper branches. Drought stressed trees are much more susceptible to attack from insects and diseases since they are lacking the vigor to fight them off and recover from them.

Control / Preventions:
Providing plants with sufficient water is by far the most important factor in keeping them strong and healthy and free of drought stress. When a plant is deprived of water, it can succumb to numerous other problems.

Monitor rainfall by using a rain gauge or even a bucket to have some idea of the moisture levels in the soil. Generally 1-2" of water a week is sufficient, but the required amount can depend on the soil type, maturity and size of the plant. Heavy soils such as clay, hold moisture much better than sandy or lighter soil types. The use of mulches will help retain moisture and regulate soil temperatures. New plantings will require regular watering and as plants mature and become established, watering needs will be reduced as their root systems are much more extensive. However, established plants cannot be neglected and still require water especially during hot, dry seasons. Inspect plants for signs of drought stress throughout the season. Using plants such as dogwoods, hydrangeas, forsythias and herbaceous perennials, which show signs of drought early, can be used as indicator plants.

Do not fertilize or prune plants during drought conditions as this puts plants under further stress.