Trees…the Ups and the Downs

By Sarah Vogt, Conservation Manager

I often find myself admiring large, beautiful trees while in the field for work or out with my family. Almost every time I catch myself viewing the tree the same way--standing under it, looking up at the canopy in awe. You may have found yourself in a similar position, thinking to yourself “what a magnificent creation.” But, what we often forget to consider is the part of the tree that lies beneath our feet. It is equally amazing and far more mysterious than the branches overhead.

What do those roots look like? It is a common misconception that a tree’s root system mirrors what you can see above earth, growing as deep and as wide as the tree. Most tree roots actually grow quite shallow but extend far out from the trunk beyond the length of the limbs above. You might be surprised that 90% of tree roots grow within the top two feet of soil and the main structural roots are in the top foot. The roots grow out from the tree reaching well beyond the drip line (end of the branches above), extending at least as wide as the tree is high, usually 1.5 times wider. It is beyond the drip line, out from under the tree, where the 60% of the absorbing root system is at work taking up water and nutrients. (See the illustration above.)

We know roots supply water and nutrients to the tree, but roots have some other tricks up their sleeves. For example, fine roots die and new ones grow on a weekly and even daily basis. When roots die, they contribute organic matter to the soil. As roots push their way through the soil, they create tunnels, which helps improve drainage by allowing water to move through the soil below ground. Tree roots can also play a role in cleaning contaminated soils, stormwater filtration, carbon sequestration, and other ecosystem services. This is impressive when you think that we are not even considering the benefits we gain from the canopies supported by all of these roots!

Fascinating, but what can you do with this information? Consider this as if you are planning a new construction project. Take a look at the trees around your building area and determine if the roots will be drastically affected. Soil grading, trenching, compaction, or the deposit of hazardous materials in the root zone could cause sections of the crown to die. The closer to the trunk damage occurs, the greater the potential for severe damage and chance of affecting tree stability.

You may also consider this information when choosing a place to plant new trees. Luckily, growing trees are opportunistic and will grow under and around existing pavement and infrastructure. The tree will find a way to grow if it is possible, but it might crack some concrete and take advantage of broken pipe if given the chance. If you are concerned about potential damage, plant the trees farther away.

For more information on tree selection and planting visit www.heartlandsconservancy.org/additionalresources.php

Other things to consider when planting new trees:

• Plant at the proper time of year. The best time is in the spring or fall while trees are dormant.

• Identify the trunk flare. The trunk flare is where the trunk expands at the base of the tree. This point should be partially visible after the tree has been planted.

• Dig a shallow, broad planting hole, 2 to 3 times wider than the root ball, but only as deep as the root ball.

• Make sure the tree roots are not circling the root ball. Cut them if necessary.

• Place the tree at the proper depth ensuring the trunk flare will be partially above the dirt level. Make sure the trunk is straight. A leaning trunk can not straighten itself out.

• Mix the removed soil with compost and fill around the tree.

• Turf grass can act as a tarp keeping water from reaching the tree’s roots. Mulch around the tree to keep soil cool and moist, but do not cover the bark around the base of the tree. Piling mulch against the bark of the tree can lead to rot and insect damage. It also creates a space for rodents to feast on the tender bark.

• Water regularly until the tree is two years old. Provide 1.5 - 3 gallons of water each week. Unless it’s really hot and dry, then increase the watering interval to 3-5 days. If the top 1-2 inches of soil are dry it is time to water again.

Metro East Tree Challenge during Metro East Tree Planting Week April 19 - 25th

HeartLands Conservancy will be working with local communities to plant over 300 native trees, which are important to support wildlife, clean air, and to reduce stormwater flooding. During Metro East Tree Planting Week, residents in the region are encouraged to plant their own trees on their property as well. Property owners are encouraged to report back to us with the type of native tree planted and a photo so we can add you to our total count! Post on Facebook or email to pictures to photo@heartlandsconservancy.org.