Gun-Shy About Trees?
September 8th, 2011
Those post-Hurricane-Irene pictures of toppled trees slicing into houses was enough to make anyone cringe.
Now that most of the carnage has been chain-sawed and chipped away, the question is what to do about all of the now-treeless spaces.
Hurricanes and tornadoes always seem to breed a reluctance to replant out of fear that a new tree today is a living-room-crasher tomorrow.
Tree companies typically even see a post-storm surge in cut-down requests from people worried about “the next time.”
That fear is understandable.
Many trees are dangers waiting to happen. They’re usually the result of poor selection, lack of good tree care and the biggie – planting way too big of a species in a small space near a target.
The sad part now is that people may over-react and become gun-shy about planting any tree anywhere.
The truth is that the threat of storm-related tree trouble can nearly be eliminated if we’re smarter about what we plant, where we plant them and how we care for them.
First, before you automatically decide, “No more trees,” weigh the benefits a tree delivers against the liabilities.
Trees give us cooling shade to make our patios usable in summer and reduce air-conditioning bills.
In winter, evergreens planted along the west and north borders can block wind and reduce heating bills.
All trees filter the air we breathe, trap carbon and produce oxygen.
They offer food and shelter to wildlife.
They give us privacy and screen out unwanted views.
And they give us beauty and the health benefits that come merely from being surrounded by trees – proven repeatedly in medical studies.
Assuming any of those are important to you, the next trick is getting the right tree in the right place.
A sugar maple is a beautiful native shade tree, but 10 feet from the house is not the place for it.
People like river birches for their fast growth and peeling bark, but it’d be a mistake to plant one under the front-yard power line.
And oaks, katsuras, sweetgums, blackgums and beeches are all worthy choices – but not if you’ve got a tiny city lot.
Bottom line: Pay attention to those size labels. Don’t pick by how big the tree is now or whether you just like the looks of it.
Find out its mature height and width and don’t plant it any closer than that to your house, sidewalk, street or kids’ play set.
If you’ve got a small or mid-size lot, go with small to mid-sized trees. There are plenty of choices. See below for 10 of my favorites.
Ditto planting around power lines. Stick with short trees under and around lines, and prune any big trees you’ve already got so they don’t drop branches on the lines during a storm. Note: Shearing and topping is NOT pruning!
The species of tree you pick also makes a difference.
The University of Illinois did some interesting research into what makes some trees more likely to fall down or crack apart in a storm than others.
Three key findings:
* Growth habit matters. Species with broad crowns and long branches (i.e. elm, hackberry, ash and honeylocust) are much more likely to crack than more pyramidal trees with shorter, stockier branches (i.e. ginkgo, stewartia, black walnut, Kentucky coffee tree and most evergreens).
* How well attached? Some trees have much stronger branch attachments than others. ‘Bradford’ pears, white pines, red maples and white birch are among the weaker-branched species that tend to crack apart more often than crabapples, dogwoods, hornbeams and sweetgums. (See http://georgeweigel.net/favorite-past-garden-columns/trees-shrubs/muscle-trees for more on “muscle trees.”)
* Speed hurts. People might like fast-growers (“I want to see it amount to something before I die”), but that rapid growth usually means less dense wood that cracks easier. Poplars, willows, ‘Bradford’ pears and silver maples are high on this list.
The final piece of the safety puzzle is keeping trees healthy.
Part of that also relates back to the site. Besides watching sizes, match a tree’s needs to the site you’ve got. That includes sun vs. shade, wet vs. dry and good soil vs. horrid clay.
At planting, get the depth right. You should be able to see the base of the trunk slightly flare out just above grade. Otherwise, you may be planting too deeply, which can rot roots and weaken trees prematurely.
Remember, a healthy tree in a happy spot is much less likely to fail than a stressed one.
Once in the ground, these steps will lessen tree failure:
* Don’t over-fertilize. Most trees need far less fertilizer than people assume. Overdoing it can lead to too-fast growth which can increase the odds of failure.
* Prune properly.Good cuts thin out the canopy and reduce the “sail effect” that otherwise increases the wind’s blow-down force. Bad cuts can create weak, excess new growth or wrongly distribute too much weight to the branch ends, which makes a tree more prone to blowing over.
* Keep mulch off the bark. Three to four inches of wood mulch over the roots is plenty, but mulch on the trunk can rot the bark and kill a tree.
* Don’t cut roots or scalp exposed ones with your lawn mower. Avoid using herbicides around roots, too.
* Water deeply once a week in a drought.
* Call a certified arborist to have a tree’s health assessed if you notice a tree leaning; the growth of flat, shelf-like fungal growths on the trunk or roots; dying branches; leaves smaller than they used to be, and any signs of cracking, peeling bark or decay.
Three good sources for more tree-care information:
The Arbor Day Foundation at www.arborday.org.
The International Society of Arboriculture at www.treesaregood.org.
Pennsylvania’s TreeVitalize program at www.treevitalize.net.
Don’t be gun-shy. Plant wisely, but plant. Late March through May and Labor Day through the end of October are the year’s two best planting windows.
Ten good small trees for small lots:
* Stewartia. The American, Japanese and Korean types are all slow-growing trees with white early-summer flowers, spectacular fall foliage and peeling bark. 20-25 feet tall, 16-18 feet wide. Full sun to light shade.
* Kousa dogwood (Cornus kousa). Slow-growing Chinese relative of the more common but trouble-prone American dogwood. Gets white or pink late-spring flowers, red-orange fall fruits and flaking bark. 25 feet tall, 18 feet wide. Sun or part shade.
* Crape myrtle (Lagerstroemia). Many varieties now sold in local garden centers are reliably hardy to our winters. Trees bloom in lavender, white, pink or cherry, and many have flaking bark and red-gold fall foliage. 12 to 20 feet tall, 10-15 feet wide. Full sun.
* Crabapple (Malus). Small fruiting tree with white, pink or rose spring flowers and red or orange fall fruits. Newer types have berry-sized fruits and improved disease resistance. 16 to 18 feet tall and wide. Full sun.
* Hophornbeam (Ostrya virginiana). Durable small native tree with small nutlets and yellow fall foliage. Tolerant of damp soil. 25-30 feet tall and wide. Sun to part shade.
* Witch hazel (Hamamelis). Small ornamental tree with very early orange or yellow flowers and neon gold or yellow fall foliage. 15-20 feet tall and wide. Full sun to part shade.
* American fringetree (Chionanthus virginicus). Native tree that gets confetti-like hanging white flowers in May and yellow fall foliage. 18 to 25 feet tall and wide. Sun or part shade.
* Cornelian cherry dogwood (Cornus mas). A little-known but durable dogwood that flowers yellow in March, then gets red fruits in fall. 18-20 feet tall, 15 feet wide. Sun or part shade.
* Sweetbay magnolia (Magnolia virginiana). A slow-growing native magnolia that does well in shade and damp soil. Gets large white, fragrant flowers in May. 18 to 20 feet tall and wide. Part shade to full shade.
* Serviceberry (Amelanchier). A native tree with white May hanging bell-shaped flowers, followed by edible blue berries that ripen in June. Most varieties have brilliant red-gold fall foliage. 20 feet tall, 15 feet wide. Sun or part shade.