There are still a few weeks until the leaves begin to change color but this week, in the wake of tropical storm Irene many had already browned, died and made their way to the ground all around the Island. Along the trails at Wasque Reservation, what was a swaying panorama of pale green brush last Friday is now a cheerless vista of brownish-gray tinder. In town centers, trees are dropping crunchy leaves onto streets and cars, and the steady hum of leaf blowers can be heard. It’s the result of what is known as salt burn, caused by an aerosol-like mist of salt water kicked up by the storm. But Polly Hill Arboretum executive director Tim Boland says however unsightly, it poses no threat to Island vegetation.

“We’ve had quite a few calls from people asking, are the trees going to die?” he said this week. “They won’t die. What happens is new leaves won’t emerge at this stage of the year. Any time after July 15 most trees, including nonnative trees, have already photosynthesized and gathered up their food reserves for the following year, so anything dramatic that happens isn’t stopping the tree from ultimately being successful and leafing out the following season.”

Mr. Boland said the mechanism for the premature browning is dessication and that some plants are more susceptible than others.

“In this case what happened was there was very little rain associated with the storm so the salt didn’t wash off,” he said. “It draws the moisture out of the leaves and essentially burns them. It’s pretty fascinating here at the arboretum to see what plants were more affected than others. Some of the tallest trees growing at the arboretum and around the Island are called tulip poplars. They’re a real good example of a tree that has a susceptible leaf to burning. What gives things susceptibility is what’s called the epidermis, and the epidermis is always covered naturally by what’s called epicuticular wax. That wax for the most part stops the leaves from losing moisture just on a day-to-day basis.

When the trees first leaf out in the spring they don’t have it and they’re very vulnerable and you can notice it — they’re strikingly green. They take on a dull coloring over the year because of the wax. Some trees, native oaks, particularly the black oaks, have a shiny, real waxy leaf. The thicker the wax the more protection it offers so our black oak trees are actually pretty tough. They recover from salt very well.”

Unfortunately, the greatest casualty may be to the annual sunset hues of Island vegetation.

“We may not have as good a fall color for certain trees but they’re still standing which is good,” Mr. Boland said.