Tree Facts: Drought conditions and your trees
The current drought conditions in western South Dakota started back in 2010. Such conditions are not unusual for the area as the native prairie vegetation evolved and adapted under alternating feast or famine moisture conditions. The only trees and shrubs that grow naturally occur in the higher moisture areas of the landscape such as drainages, creeks and rivers. However, even those trees are not totally immune to drought.
So, how are your trees affected? The primary affects of drought or dry soil conditions cause damage to the roots and root death. The non-woody feeder roots located in the upper 18 of soil are the first ones affected. Transplanted seedling trees are particularly affected due to root loss during the transplant process. It is common for seedlings from the nursery to have lost up to 50% and larger balled and burlapped trees up to 80% of their roots. So, transplanted trees have to play catch up in order to become established.
Transplanted trees are under stress due to the loss of roots. It can take up to two years for tree seedlings to become completely established. The rule of thumb for bigger transplanted trees is one year for each diameter inch of the tree trunk. As a consequence, these trees should be given extra care and attention during drought periods. This includes watering and mulching under the tree to provide much needed moisture, decrease evaporation and cool the roots.
Symptoms of drought on trees show up in a variety of ways depending on the tree species, soil conditions and water deficit. Reaction time of trees is slower than what we might expect and may take many months or up to a year to be noticeable. Leaves and needles become limp, drooped, wilted, curled, yellowed and may drop prematurely. The trunk and or branches may exhibit splitting, bark separation, tip dieback and sucker type sprouts may occur down lower on the branches or trunk. Leaves of broadleaf trees become scorched along the edges and the inside of the leaves may turn yellow then brown. Needles on evergreens turn brown on the tips or appear off colored. As a result, the foliage of trees may become much thinner than normal.
In extended droughts additional problems may occur due to the weakened condition of the trees. They become easy prey for boring insects, root rot and fungal diseases which combined with the effects of drought can kill the trees. These secondary problems can take up to a year to develop and may be prevented if supplemental watering and care is provided.
Besides dry conditions, high temperatures can take a toll on trees. Temperatures above 95 degrees slow biological functions of trees. Trees may lapse in and out of a self induced dormancy in efforts to reduce water loss. However, the slowing of the functions of the tree also reduces the amount of plant food produced and stored by the tree. Therefore, in high temperature periods of drought a tree can be declining from its need for moisture and food.
Planting native and introduced trees and shrubs are not fool proof but they do provide a better chance of surviving the hot dry conditions that occur during droughts. Some drought tolerant species for our area include SHRUBS: Silver Buffaloberry, Caragana, Honeysuckle, Potentilla, Hansen Hedge Rose, Arnold Hawthorne, Silverberry; BROADLEAF TREES: Green Ash, Siberian Elm and Bur Oak, and EVERGREEN TREES: Rocky Mountain Juniper, Eastern Red Cedar and Ponderosa Pine.
My sources for this news release were St. Vrain Arbor Care, Michigan Extension Service and Texas Extension Service. If you would like more information about Drought Conditions and Your Trees, contact Bob Drown at the Conservation Office at 605-244-5222, Extension 4 or by e-mail at email@example.com.