Winter Pruning Temperatures
By Lynn E. Long
With the early cold weather that we are experiencing you may be wondering how recently pruned trees will respond to these cold temperatures. (Read this to learn how cold affects fruit buds.)
When a pruning cut is made, there is an invigoration of the tissue around that cut making the limb somewhat more cold sensitive than non-pruned limbs. The greater the percentage of wood removed the greater the stimulation to the tree. Therefore, big cuts and cuts on young trees are potentially the most hazardous cuts. In addition, special care should be taken to avoid pruning old, weak trees immediately before or during intense cold. Cold sensitivity seems to last for a period of about 10 days. As time passes after the cut was made, the tree becomes less and less sensitive until it regains its former hardiness level approximately 10 days after pruning.
Generally speaking, if your pruners can stand the cold, so can your trees. However, constant, moderately cold temperatures like we’ve had the last few days are generally not the problem. The greatest problems occur when temperatures drop quickly, especially, if the temperature has been moderate or warm for a period of time. It is at these times that you want your trees at the maximum cold hardiness possible. It makes sense, therefore, not to prune immediately before a cold spell is predicted. The best way to be safe is to keep your eye on the long range forecast. If near 0° F temperatures are predicted, all pruning should stop at least 5 days before the cold weather is expected.
It is also important to carefully plan your pruning. Since young trees are more sensitive than large trees, plan to prune your healthiest, mature blocks at the time of year when cold spells are most likely to occur.
- Pruning causes a brief period of decreased winter hardiness
- Large cuts and cuts on young trees are potentially the most hazardous.
- If near 0° F temperatures are predicted, all pruning should stop at least 5 days before the cold weather is expected.
Lynn E. Long is an Extension Hortliculturalist with Oregon State University