Yesterday, we heard from Scott Merkle, professor and associate dean of Research at the Warnell School of forestry at the University of Georgia in Athens on his research on hybrid sweetgum trees. Quality sweetgum is a desirable product to feed the pulp and paper mills of the southeast, and the tree isn’t choosey about soil and water availability. One of the benefits of a sweetgum stand, is that once the mother tree is harvested, many, many more take their place. This would mean that, theoretically, the trees would only have to be planted once:
“Ideally, yea. And that’s what you think coppice forestry should work, and it does work with things like poplars. To best of my knowledge, what is missing, is the type of harvesting equipment that you need to deal with the coppice, that is you know, when you cut down one sweetgum tree, you don’t just get one new sprout that comes up, you get a whole bunch of them.
So, there has to be some way of dealing with all the extra sprouts, and whether that’s harvesting all of them, or trimming away all the extra ones that aren’t that great and keeping the one you want, I don’t know if that’s really been determined for a coppice sweetgum stand or not.”
When we think of sweetgum trees, we think of huge leaves, fabulous fall color, and those nasty little ‘gum balls’ that seem to show up everywhere. But the type of sweetgum that Merkle is working with is a bit different;
“What I’d like to get across, is that these are somewhat different trees than regular old sweetgum trees. They look kind of like regular sweetgums, in that the leaves look like sweetgums in that the leaves have five lobes that kind of look like a star, but you can tell they’re hybrids because the tree that our American sweetgum was hybridized with was the Chinese sweetgum, or people call it the Formosan Sweetgum, which looks a lot like our sweetgum, but has a three-lobe leaf. So, you can actually tell the hybrids apart because the leaves look like they have three lobes with two extra bumps on them, they’re intermediate between our regular sweetgum and the Chinese sweetgum. Other than that, they look a lot like the American sweetgum.”
In his work to discover a hybrid sweetgum that was both sturdy and fast growing, Merkle stumbled upon some other hybrid mixes that could have a place in the landscape:
“I think what’s really interesting that we were able to hybridize these two species sweetgums that have been separated from each other for 10 million years of continental drift, and they’ll still make these vigorous hybrids.
The other thing I’d like to say si that not all the clones we generated, are these great, fast-growing trees. There’s always going to be variations, so in my little test planting, I have some trees that have grown really fast, like the ones that are being marketed, but I also have some beautiful, little hybrids like dwarfs, and intermediate trees that would make really nice ornamental trees that have color. So, there’s other uses for the hybrids besides the pulp and paper industry.”
For producers that are interested in learning more about producing hybrid sweetgum trees for commercial cultivation, Merkle has this advice:
“The main thing is that people that are really interested in finding out more about the performance of the trees and how to get some, should contact my collaborators at ArborGen, they’re now the ones that are propagating them, and marketing them.”
University of Georgia’s Scott Merkle.