ILLINOIS
YARD & GARDEN
  Fast Growing Trees The First To Go
How to chose the right tree for the long term
David Robson
Extension Educator, Horticulture, at the Springfield Extension Center, University of Illinois Extension.

We tend to think of trees as majestic plants that will be around for decades if not centuries. Yet, in an instant, limbs and trunks can come crashing to the ground.

That happened the first day of December 2006, and was followed by another losing bout with ice on January 12 of this year. It’s hard to imagine that just a little ice can wreak havoc on something that just hours before, while not fully leafed out and providing shade, was still acting like a sentinel over your domain.

In Springfield, we additionally suffered two tornadoes over the past year. Jokingly, we say, “well, at least everything dead and weak is gone, so our trees are good to go for another decade.” That could be partially true, but at the same time, who knows what curve nature will throw again?

Even horticulturists who should know better aren’t immune. My gorgeous Heritage River Birch, with its ornamental peeling bark, lost four of its eight tops between December and January. More probably would have been lost, except those branches actually were lying on the roof, so they couldn’t snap. The advantage of pushing a tree with fertilizer and water to grow at least 3 feet a year came back to bite me in the rear, hard.

Fortunately, a certified arborist who knew what he was doing did some major tree work. It will be interesting to see what happens this spring and coming year. At least the tree is there.

Still, every other tree stood proud and tall. That’s because they all are slower-than-molasses at growing, so the wood was strong and the leaders dense with side branches equally spaced. They might have bent a bit, but sprung back in place.

Which brings up all the trees that didn’t.

Sure, some oaks and sugar maples had damage, but in most cases, they just stood and looked while their neighbors suffered more factures than some falling down a ski slope. Obviously, the birches with their weak wood and multiple leaders fell apart. Silver maples weren’t far behind, followed by poplars (including cottonwoods), redbuds (usually the older ones), pines and spruces, but more of the former and ornamental pears.

When you look at the damaged trees, a couple things come to mind.

First, fast growing trees are more prone to storm injury. The wood isn’t strong and trees only have so much flexibility. The slower the tree grows, the harder the wood, and the less damage.

The branching structure is one of the most important aspects of bearing up under wind and ice.

We talk about crotch angles – where the limbs join the trunk. The ideal angle is between 45 and 60 degrees. Many fast growing trees, and noticeable on just about all silver maples and Bradford pears, have angles closer to 20 or 30 degrees. That means lots of included bark, which is bark that looks like it’s grown together but hasn’t. It’s usually the line of bark that extends down from what appears to be the joining of the limbs. This is usually where limbs snap because there’s no structural support.

You can weigh limbs down, or use spreaders, to better create that angle, but you need to do it in young trees instead of older ones, which resist the spreading.

Some trees are just naturally old and were just hanging on. Like people, trees age. Redbuds get old and actually provide more garden interest with their gnarly trunks and oriental-like shapes. Unfortunately, the wood isn’t strong any more and branches break.

Other limbs and trees were hollow. Hollow trees can stand for years and years, but without the inner strength of the wood, don’t have the ability to counter the extra weight of ice.

Finally, trees weren’t balanced. In other words, when looked at from a bird’s eye view, the trees weren’t rounded. What was on one side of the tree wasn’t balanced on the opposite side. So, as the tree was blanketed with ice, more weight was bearing down on certain parts of the tree instead of others. The results were toppled limbs and trees.

Next month, in honor of Arbor Day, we’ll take a look at what types of trees should be planted.

 

For more information:

check out the University of Illinois Web site at: www.ipm.uiuc.eduYou can contact David Robson via E-mail: drobson@uiuc.edu

Or write to him in care of:

Illinois Country Living
P.O. Box 3787,
Springfield, IL 62708.

Telephone: (217) 782-6515