A program was held on Monday, May 21st*, on pruning young trees for structure and selecting quality trees for planting. We discussed the importance of evaluating the structure of trees’ trunks, canopies, and root systems. The root system is often overlooked.
Prior to selecting trees for an installation, take some time to inspect the roots. This could mean removing trees from their containers or removing excess soil from the top of the root ball. Plants and trees, especially those grown in containers, may have several inches of excess soil on top of the root ball. This should be removed, as you want to ensure that the topmost, or first-order root(s), is about 10% the height of the root ball above grade after planting. Over time, the tree will settle and the topmost roots will be at grade. This allows the root system to grow properly, and to receive enough water and oxygen to support the growing tree. Planting a tree too deep and/or failing to remove excess soil from the top of the root ball, is a common cause of tree decline.
A healthy, structurally sound root system has roots that grow straight, away from the trunk, and do not circle or girdle. Trees that have been planted too deep, or left in containers too long, may develop circling or girdling root systems.
When roots hit the impervious container, they turn and begin to circle the pot. This can be a huge problem in the landscape: as the tree matures and the canopy grows larger, the roots continue to circle, possibly girdling the trunk. They may not be able to support the tree – failure is a possibility.
Sometimes circling roots will be very fibrous – these can be teased out prior to planting or sliced with a sharp shovel after planting.
When circling roots have turned woody, pruning can correct these defective roots. Pruning cuts should be made before the root turns, as new root growth will be in the direction of the root just before the cut. I encourage you to make a commitment to planting trees with the topmost roots just above grade, and to inspect root systems prior to selection and planting.
*(This program was the first of eight in the 2012 ‘Strengthening our Community Tree Canopy Series‘ for professionals, a project supported by FDACS and the Florida Forest Service through a 2011 Urban and Community Forestry Grant. To learn more about upcoming topics in this series, Download the 2012 Urban Forestry Brochure here.)