Forest
Stewardship News Release
June
7 , 2006- For Immediate Release
Contact: Allyson
Muth , Phone: 814-863-0401 E-mail: abm173@psu.edu
Trees and Drought
Written by Bill Elmendorf, 814-863-7941, wfe1@psu.edu
Adequate water is crucial for tree growth. Water is one of the main elements involved in photosynthesis. Without water trees cannot produce enough food to fuel growth. Drought impacts the leaves' ability to produce food, the roots' ability to grow and function, and the plant's ability to move food, hormones, and other elements around. The main problems associated with longer periods of drought (weeks and months) are poor and stunted growth. Ultimately, lack of water will lead to death either by desiccation and starvation, or secondary problems such as a soil fungus. Some trees (e.g., beech and dogwood) are more sensitive to drought than others (e.g., gingko and redbud).
Symptoms of drought include wilting of leaves for a number of days (especially those exposed to afternoon sun and wind). All trees leaves can wilt on especially hot days, but they should recover quickly in the evening. Ultimately, long-term drought will cause browning of leaves, loss of leaves, early fall coloring, poor and stunted growth, and death. Interestingly, the symptoms of overwatering are the same as drought due to the negative impacts too much water has on root growth and function.
Treating drought is
not just about applying water. There is more to consider:
1) Treat any cultural problems such as soil compaction, soil fill, deicing
salts, weeds and turf, and root damage.
2) To slow evaporation of water and control weeds and grasses, mulch as
much area under the canopy as possible with 2- 3 inches of composted mulch.
Keep mulch a few inches away from the tree trunk. Instead of mulching,
protect the natural leaf litter - it serves a similar function.
3) Apply moderate amounts of water slowly and deeply so that water supports
good plant growth, but does not exclude oxygen from the soil. There is
no absolute rule on how much water to give trees. The need for irrigation
is affected by tree species and size, soil/site conditions, and weather.
Trees, young or old, need water to penetrate from 24 to 36 inches into
the soil. Soil must be allowed to dry between watering. Newly planted
trees should be watered every four days or so during hot, dry weather.
This means applying about 10 gallons deeply through soaking. Two rules
of thumb for older trees are: 700 gallons of water per 1000 square feet
of tree canopy and 20 gallons per inch of diameter. In both rules water
is applied deeply and slowly through soaking. These are huge amounts of
water, and in most cases it is not possible to irrigate large areas of
trees. Mature trees benefit from irrigation when they have been hurt by
soil compaction or root damage, or are especially valuable.
Periods of drought are to be expected and seasonal water stress is part of our growing season. But, even in Pennsylvania, newly planted trees must be irrigated; root growth and food manufacturing stops, or is greatly lessened, in dry soils. Two actions that will absolutely NOT HELP in drought are fertilization and pruning. Do not do these!
The Pennsylvania Forest Stewardship Program provides publications on a variety of topics related to woodland management for private landowners. For a list of free publications, call 1-800-235-WISE (toll-free), send e-mail to , or write to: Forest Stewardship Program, Forest Resources Extension, The Pennsylvania State University, 320 Forest Resources Building, University Park, PA 16802. The Pennsylvania Bureau of Forestry and USDA Forest Service, in partnership with the Penn State's Forest Resources Extension, sponsor the Forest Stewardship Program in Pennsylvania.
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