Saturday, October 27, 2012
Once upon a time Freeman made a maple
Species name: Acer x freemanii
Common name: Freeman maple
Technically speaking, the Freeman maple isn't actually a species at all, but rather a hybridization between a red and a silver maple that happens often in nature when the two species are present in the same location (which is often; their native ranges overlap almost completely). Depending on whether it's silver maple pollen or eggs, you can get drastically different phenotypes (or appearances of the tree). I'm betting that this tree was produced as a result of red maple pollen and silver maple ovules (eggs); the characteristics of this tree are almost identical to the silver maple except for the bright red petiole of the leaf. In fact, this tree is labeled as a silver maple on campus, but I have my doubts. If it was truly a silver maple with no hint of a hybrid, it would have green petioles and would be turning a yellow-green in the fall, not red.
So why would you want to hybridize a red and silver maple? Well, the silver maple grows very quickly, and so provides shade to an area faster than a red maple would which is often a desirable outcome of planting a tree. The downside of the silver maple is that their roots can often be quite invasive. They don't grow very deeply into the soil, and can bubble up concrete or asphalt easily which is not always a desired outcome. The red maple has much deeper roots that don't creep along the soil surface, so there is less of a chance of destroying nearby sidewalks, roads or driveways. The wood of the silver maple is also incredibly brittle. Normally this doesn't matter since many people enjoy the tree and not the lumber at the end of the day, but silver maples also have another dirty secret: they're almost always hollow due to heart rot (a fungal disease where the fungus targets the old, dead wood on the inside of the tree that is used for support). This is great for wildlife who require hollow trees to nest, but terrible for your house or garage during a wind storm; trees shown on TV that have crushed cars or houses after a violent storm (not a tornado) are often silver maples. This doesn't happen with red maples. Their wood is much more durable, and they are less likely to get heart rot and so are less likely to be destructive during a bad storm. The last reason why you might want to hybridize the two species is because of the aesthetic factor; bright red petioles are much prettier than just plain old green ones. Depending on the number of generations since the initial hybridization, the leaves might also turn a brilliant yellow-orange during the fall instead of the silver maple's boring yellow-green. You never quite achieve the neon red of the red maple's fall coloration, however.