Anyone who has lived in Colorado will tell you, the weather here is crazy! When heavy spring snow hits, significant damage on established tress is a dire possibility. Cottonwoods, poplars, willows, green ash and elms are particularly susceptible to breakage because they have softer wood. However, with high enough wind speeds or heavy enough snow loads, no tree species are risk free. Keep reading to find out what you can do to repair your woody friends.
The tremendous leverage that wind and snow exerts on tree limbs causes various types of damage which typically include broken tops out of conifers such as spruces and pines to torn and twisted limbs on deciduous trees. This type of damage rarely heals well by itself, which makes immediate pruning essential if the tree is to be saved and allowed to regain its former beauty.
For different trees will sustain different types of damage. In each case it is important to properly treat the different types of damage a storm can cause to give the tree a chance to properly recover. The first goal of pruning injured branches is to minimize the amount of woody tissue exposed to the air. Open wood is an invitation to pests and pathogens to enter the tree and further damage it. Injuries cause by twisted and broken branches need to be trimmed in such a way that the tree is able to heal over the wound as quickly as possible.
The jagged injury created by a broken branch will heal very slowly since new bark has to grow over the injured area from the surrounding healthy bark. Any kind of irregular surface will act as a barrier to this new bark growth (called a callous). A smooth surface made by a proper saw cut will allow bark to cover the exposed wound much more quickly. It is equally important to prune branches back to an area of healthy tissue that will remain alive. If a break occurs near the main tree stem or close to a larger branch, the broken branch should first be removed to reduce the weight and leverage on the healthy wood. Next, the branch should be trimmed back close to the main stem at a slight outward angle as shown to ensure that enough healthy tissue surrounds the cut to promote healing. Under no circumstances should a short section of branch be left on either a branch or along the main stem that is long enough to “hang a coat on”. Poor cuts will result in a dead “stob” protruding out of the side of the branch or stem that will die off allowing decay fungi and insects to attack the woody tissue inside the tree.
Another type of injury is referred to as a “split” limb. This is caused by a twisting motion. Severe splits will cause the rest of the branch to eventually die and also create a hazard to anyone or anything under the branch. Some splits have a good chance to heal. To help diagnose if this type of injury will warrant the removal of the branch, consider the following:
- Is the twisted limb in a place on the tree where its removal will severely affect the shape of the tree? If not, it may be best to remove the branch.
- Does the branch flop around in the wind or does it appear to be fairly secure? As the branch moves in the wind does the split open and close? If the branch seems fairly secure and the split does not flex noticeable the branch will more than likely recover.
- Is the branch greater than 4 inches in diameter? If so, there is considerable weight on the branch and the split represents a dangerous structural hazard that can result in the branch breaking off unexpectedly.
- Does the split result in an open gap greater than 1⁄2 inch wide? Splits larger than this rarely heal, and the opening will eventually allow wood decay fungi to enter the branch and further weaken it.
- Finally, if there is no immediate danger of the branch falling off in a heavily traveled area, wait and see if the branch recovers – this should only apply to a branch that is split but has not changed its structural position much (not hanging crooked).
When removing a split limb, it is important to follow the proper cutting procedure. Since the limb is already split, improper cutting can cause the split to enlarge and potentially cause much more serious damage to the tree. Also, cutting directly through split will often bind your saw creating a dangerous situation.
Sometimes trees are injured to such an extent that tree removal and replacement are the best options. Making such a decision should be based upon the tree species involved and what the tree owner desires. Some tree species such as willows, cottonwoods, green ash, and Siberian or Chinese elms can virtually grow new branches from a stump. The advantages of such a situation are that you will have a tree (of sorts) back fairly quickly. The disadvantage is that the tree will more than likely develop serious internal wood decay that will structurally weaken the tree if it allowed to get too big.
Although resprouting often appears, there is no prediction of how vigorously this will occur. In such circumstances it may be best to prune back broken limbs and trim wounds as best as possible, then wait for one year to see what type of regrowth occurs. Where sprouting occurs on branches that have been broken off, selective pruning after one year should be used to allow a few select sprouts to develop into branches that will fill the gaps left by removed limbs.
Evergreen trees need to be pruned slightly differently than broadleaf trees. Typically a conifer will have one main stem with whorls of lateral branches evenly spaced along the stem. Lateral branches do not resprout as well as most hardwoods, although there is some variation among species. Spruces, and firs may produce some weak new lateral branches, whereas pines will rarely grow new lateral branches. All conifers will produce new leaders (tree tops) if they have enough lateral branches left to support such growth. Typically a conifer that has lost all of its branches will die.
Conifers that have lost their tops to a wind storm should have their main stem trimmed back to within an inch or two of healthy lateral branches. The final cut should be made at a slight (10°) angle to allow water to run off, especially after new callous growth forms a ridge around the edge. Typically, several new leaders will start to form from the lateral branches nearest the top. If left unchecked, the tree will develop multiple tops which over time will create a tree very prone to further wind damage.
Several options are available depending on the type of tree and maintenance the tree owner desires. Multiple tops on spruces will not hurt the tree if these tops are pruned on an annual basis keeping the tree short and rounded much like a hedge. If the desire is to let the tree get tall again, it is highly recommended that the strongest new leader be selected that is closest to the original stem. Eventually it will be difficult to see where the tree was broken except a small crook where the new leader took over. This procedure is recommended for pine trees as in most cases they do not respond well to annual pruning. Fir trees are somewhat intermediate between spruces and pines in their response to pruning.