I'm a schvitzer. I don't perspire delicately. If it's over 70 degrees, I sweat. Profusely. Making everyone around me almost as uncomfortable as I am. I once had a client from L.A. who would jet in to NYC every month, cool (in every sense of the word) and schvitz-free in his expensive suit, even in the middle of August. He was fascinated by my sweatiness. I felt uncouth just looking at him.
But at least I CAN sweat. What can a poor tree do? When it's too hot to garden, it's tough on our container trees. They have comparatively little soil to insulate their roots, and the unrelenting sun beats on their container walls day after day after day, heating up not only the soil surface, but warming the rootball from all sides. When it's 90 degrees on the rooftops I'm not the only one who's suffering.
Last month I started noticing a pattern, primarily among the container trees growing in full sun. The leaves were starting to change color. A lot of gardeners have noticed flowers blooming early this year, but it was the red leaves on the viburnum and the ripening holly berries that made me sit up and take notice. Fall foliage in August!? Does that mean bare branches in September?
My shady gardens (and by my, I mean my clients') are pretty much normal, but the container plants in full sun are ahead of the calendar. I suspect it's the hellishly high temperatures, of both soil and air. Schvitzing is a cooling mechanism that helps my body deal with the heat. But when a tree's roots get overheated and nighttime temperatures offer little respite, what's a tree to do? Drop a few leaves, I guess.
Of course I'm just speculating. But I like to think that years of field experience combined with some solid book learning has given me the tools to figure this out. To that end, I'd like to expand my data set. Have any of you noticed a similar trend? Can you contribute to my theory?
On Friday, we two Ellens depart for the annual Garden Writers symposium in Dallas. (Talk about schvitzing...who thought Dallas in September was a good idea?) I plan to survey as many GWs as possible about this problem, and I'll also be looking for suggestions on TLC for heat stressed container trees. It's not their fault they can't sweat.