Trees and Construction

Building your dream home on that wooded lot

By Amy McDowell

Wooded residential lots cost thousands more than treeless lots, but if those trees aren’t protected during construction, they can be severely damaged. Often the damage isn’t visible and the slow physiology of trees means they may live for four to seven years after construction crews have left the site, slowly spiraling into decline and finally death.

Soil compaction from heavy equipment and building materials is the most common damage. Ninety percent of a tree’s roots are within the top twelve inches of soil. Soil compaction may crush or tear the fine roots, but the loss of air space within the soil profile can be long lasting and even more devastating. Soil organisms can take decades to loosen compacted soils and return them to a healthy environment for tree roots.

The most important step to protecting the trees on your building lot is to ring them with a barrier that is not easily moved by construction crews. Metal stakes and bright orange snow fence works well. Place the barrier at least one foot from the base of the trunk for every inch of trunk diameter. For example, a tree with a two-foot diameter trunk must have a barrier at least 24 feet from the trunk.

Even after construction is complete, continue to guard the root zone. Don’t let a finish grader add or remove soil within the barrier zone. If you seed or sod the new lawn, use care not to drown the tree by irrigating too frequently. After the turf is established, water no more than once or twice a week.

A three-inch-deep mulch ring around the tree will protect the trunk from mower and string trimmer damage, and the wider the ring the better it is for the tree’s roots. Some arborists say a mulch ring that runs clear to the drip line of the branches would be a tree’s dream-come-true, although they realize that much mulch is unrealistic for most homeowners.

For large construction sites with complicated traffic patterns around trees, you might want to consult with an ISA certified arborist on how best to protect the trees. Information is available at www.isa-arbor.com or 800-ISA-TREE.

How NOT to trim a tree

Tree Topping is a Tragedy

By Amy McDowell

“Forfeit his hand, he who beheads a tree.” John Evelyn, Sylva, published in 1664.

Those words were written 347 years ago, but incompetent morons are still topping trees today. My heart lurches with horror when I see a tree butchered like the one in this photo.

(Photo by Larry Costello)

Trees do need pruning from time to time, but they NEVER need a severe heading back or topping. In fact, a tree will never fully recover from being topped. It will scramble to replace all of that food-producing leaf surface, but the rapid new growth is always weaker.

“Don’t do big, drastic pruning once every 15 years,” says Dr. John Ball, a professor of forestry at South Dakota State University. “Tree care should be life-long and low-intensity.”

At a recent arborist conference, Ball shared his advice on tree care. Training young trees is ideal, because you can set them up to live a long and healthy life. Most often, however, people wait until the trees are mature and then prune them. “You cannot make a tree healthy by making it smaller,” writes Dr. Alex Shigo. And over thinning the canopy, says Ball, is like bleeding a tree to death. “Branches are independent, not parasitic. Each one must produce its own food.”

ISA Certified Arborists can look at a tree and recognize what to prune. You can trust that an ISA Certified Arborist will do what is best for the tree. They sometimes laugh that their clients expect to see a huge pile of tree trimmings when they are done working. A trustworthy arborist is one who is most concerned with the safety and health of the tree and not concerned about creating a large pile of brush to impress their clients.

There are more than two dozen ISA Certified Arborists in and around the Des Moines area. You can find arborists in your area by visiting www.TreesAreGood.com.

I’d like to thank Dr. John Ball of South Dakota State University for the inspiration for this column. The photo, taken by Larry Costello, was provided by the International Society of Arboriculture.