When pruning storm damaged trees, using proper techniques to prevent damage to the branch collar will result in the speediest healing.
Gardeners in many areas of the East are reeling from the devastation caused when Hurricane Sandy ripped through just before Halloween, leaving a landscape of broken trees in its wake. High winds and flooding caused massive damage to both property and plants in some areas. Here are a few suggestions for helping your plants recover as quickly as possible from Sandy's wrath and some tips for minimizing storm damage in the future.
Think Safety First
Don't do anything after a storm until you are sure that any downed power lines have been taken care of by your local utility. It's also important to remember that large or hanging broken branches, or those high in a tree, can be dangerous to deal with on your own. It is best both for your safety and the health of your trees to have an arborist take care of these kinds of pruning needs.
Don't Rush to Judgment
Don't be in too much of a hurry to declare your tree a total loss. Trees can be surprisingly resilient. Even if a tree has lost some major limbs, it may still be worth saving. An arborist can help you decide if your tree can recover enough to continue to be a safe landscape asset.
Use Proper Pruning Techniques
To remove smaller, accessible broken tree branches, cut them back completely to where the damaged branch joins a larger branch or where it intersects with the trunk. Don't leave a stub that won't heal and will invite decay. And never top a tree by cutting the main structural branches back to stubs. This will ruin the natural form of the tree and result in a burst of weakly attached new growth that is likely to break off in future storms.
Leave the Branch Collar Intact
Trees heal by forming callus or scar tissue over their cut surfaces. To make sure this happens most readily, with the least chance of decay setting in, you want to take off a broken branch without damaging the tissue of the trunk or branch it's attached to in the process.
To do this, take a careful look at your tree before you cut. Start by locating the branch bark ridge, a raised area on the upper surface where the branch meets the trunk or larger branch. Begin your cut just outside this ridge, angling it down to the outside of the branch collar, the bulge that forms at the base of the branch where it intersects with the trunk. Leaving the branch collar intact will help the cut close over more readily.
To prevent the branch you're removing from breaking off prematurely and ripping the bark below, use a three-cut system for branches larger than a couple of inches in diameter. Several inches out from the trunk (or larger branch) make a cut up from the bottom about a third of the way through the branch you're removing. Make a second cut from the top completely through the branch a few more inches out from the first one. This will allow the branch to fall without harming the tree. Finish by removing the stub just outside the branch collar.
Don't Seal Pruning Cuts
Current recommendations are to leave pruning cuts unsealed. Research has shown that sealing cuts and wounds on trees doesn't speed healing and can, in fact, promote decay.
Repair Torn Bark
If a broken branch has left an area of torn bark, trimming back the ragged edges to leave a smooth border of healthy tissue will promote the speediest healing. A sharp utility knife is a good tool for this task. Shape the edges of the wound into an pointed oval to encourage good healing.
When you add more trees to your landscape, avoid fast-growing, weak-wooded trees like silver maple, Siberian elm, Lombardy poplar, and catalpa. While it's tempting to choose fast growers for a more immediate effect in the landscape, the tradeoff is a greater likelihood of storm damage.
No matter what kind of trees you're growing, encourage young trees to develop strong branch angles on their major limbs and symmetrical branch placement that keeps the center of gravity over the trunk. Narrow branch angles are inherently weak and more apt to break off under a load of snow and ice. When you are selecting trees at the nursery, look for ones with their main branches attached at wide angles (think 10 or 2 o'clock) and symmetrically placed around the trunk. Prune judiciously to encourage this branching habit as the tree grows.