Delaware census: Street tree do’s and don’ts
Two crews of six Delaware County Master Gardener Volunteers are hitting the streets of Delaware weekly in this, the third year of the ongoing Delaware Tree Census. The teams have completed the inventory in the central city and they are now working in the newer developments on the outskirts of town. As they progress, they have noted many beautiful, healthy trees, while others are struggling. They even encounter trees that are dead or dying.
As a homeowner, there are some things that you can do to help your street trees live up to their best potential. According to Chuck Rexode, a retired USFS research entomologist and the city’s contract forester for 22 years, the two most important things you can do are to water your trees during drought periods like we have had this summer, and to stop volcano mulching.
Many trees are stressed from lack of rainfall. Rexode noted that the situation is dire for many young sugar maple trees with sun scald. This condition occurs when water evaporates from the leaves faster than the roots take it up. Watering will help and may be enough to save the tree. Remember when you water to give the ground under the tree canopy a good soaking so the water will penetrate the ground for several inches.
Many homeowners and landscapers pile mulch around the trees. According to Rexode, this is a bad practice as excess mulch promotes fungal growth around tree trunks and then decay sets in. Also, a wet spring season promotes root growth around the base of the tree in the mulch, but these roots dry out quickly later in the season and the tree suffers since it depends on these newly formed feeder roots. The roots in the mulch can also grow around the tree trunk and end up strangling it. While you should keep mulch around a tree year-round, it should only be a couple of inches deep. The mulch helps avoid string trimmer and lawn mower damage, but it should be kept two to three inches away from the trunk to avoid encouraging fungal growth. Homeowners also should regularly remove suckers, which are small shoots that grow out from the base of the tree trunk.
Many street trees need pruning. But, Rexode cautions, “Don’t prune unless you know how to do it properly.” The city’s Shade Tree Commission is seriously considering launching a new program to help the city prune its street trees. It would be staffed by groups of trained volunteers that would prune their own street trees and/or street trees in their subdivision. This effort would be limited to trees with branches that can be pruned manually, without the use of power tools and are close enough to the ground that they can be reached without the use of a ladder.
Sometimes trees are planted at an incorrect depth and that can lead to premature decline or death. At the base of the tree where the trunk and the root system meet is the root collar, which has a slight flare. The flare needs to be exposed when the tree is planted. According to Erik Draper from OSU Extension, “Plant ’em high — watch ’em die; Plant ’em low — never grow; Plant ’em right — sleep at night!”
Landscapers or developers frequently stake new trees to ensure they remain upright. Rexode said these stakes should remain around the trees for the entire warranty period of two years. While one year would be sufficient in most cases, developers and landscapers will not warranty the trees if the stakes have been removed. These stakes should not be excessively tight and should allow for some tree movement. After the warranty period, the stakes and guy wires should be removed. If left on permanently, the wires will eventually completely girdle the tree, depriving it of nutrients, including water, and the tree will decline or die.
Delaware City is implementing a new program to increase the diversity of the street trees. The city is also paring back, but not eliminating, planting maple trees. Maples already represent a large percentage of Delaware’s urban forest. In addition, maple trees are disposed to verticillium wilt and more recently there has been the threat of the Asian Longhorned Beetle (ALB), which has been found in southwest Ohio. Since insect pests typically attack one tree genus, or family, increased tree diversity will help avoid a situation where the majority of the street trees in one community are destroyed.
As of early August 2012, Delaware County Master Gardener Volunteers have completed about two-thirds of the city’s districts in the Tree Census, and they expect to complete the project in 2013. You may see a group of “tree huggers” in your neighborhood identifying and measuring trees. Please don’t hesitate to say “Hi” or ask them a question.
Nancy F. Traub is an OSU Extension Delaware County Master Gardener Volunteer