Lessons Learned from Irma

Just about everyone in southeastern Florida was able to breathe a sigh of relief after Hurricane Irma left the area. Its 11th-hour course change allowed us to escape a devastating direct hit, and our homes were largely left intact. However, many of our trees suffered greatly, even though officially they were battered by ‘only’ tropical storm-force winds.

Tropical storms are not all alike; each one provides bits of information that help us better understand these capricious natural systems. This brief article addresses some of the lessons learned from our experience with Irma.

There appear to be at least three reasons why the landscape of southeastern Florida took such a beating from the storm:

(1) Duration – We were subjected to strong winds for a long time following their start on Saturday, September 9. Those of us who ventured out just before sunset on September 10 still experienced occasional strong gusts. Clearly wind strength is not the only variable influencing the capacity of a tree to survive; even winds of sub-hurricane strength can cause great damage if they last long enough.

(2) Pruning Practices – Lots of trees blew over or cracked up because they had not been pruned to deal with tropical storms. Good pruning opens up a canopy so that it allows wind to flow through it rather than to create resistance by acting as a sail. The most successful pruning is done over a three-year period. This is especially important if the homeowner wishes to keeping fruit trees producing every year; severe pruning performed all at once can halt fruit production for a season.

(3) Planting Practices – All over our region there are examples of trees that were planted improperly. The evidence is the exposed rootball – remarkably small compared to the size of the tree. (In one egregious instance, an upturned tree in the median on U.S. 1 was seen still wrapped by the sides of its container!) Some experts, including those on governmental sites, have been suggesting that a planting hole need only be large enough to accommodate a plant’s rootball. Richard Lyons’ Nursery respectfully disagrees, particularly with regard to installation in the limestone substrate that is so common in our area. For proper root development, a planting hole approximately 5 ft. X 5 ft. should be excavated for planting a new tree. Alternatively, good stability in high winds can be provided by digging an X-shaped trench so that roots can extend a good distance in each direction.

Please keep in mind that the planting hole need not be improved with rich potting soil; that will only serve to confine the tree’s roots to the better mix. Instead, you should backfill the hole with the poor soil and the now-crushed rock that was excavated. That will cause the tree to root out in all directions, making it more stable as it grows up. Water generously to settle the material and eliminate air pockets. Finally, apply mulch over an area that extends further than the rootball. However, in order to discourage insects from invading the plant, do not pile mulch against the stem. Leave an area open 6-8 in. around the stem so that air can circulate.

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