Trees that have been planted too deep are, unfortunately, a very common problem in the urban landscape. How can you tell if your tree is planted too deep?
First, a quick lesson in tree biology
Trees aren’t supposed to look like telephone poles sticking out of the ground. They are supposed to have a taper or “flare” at the bottom. The flare helps anchor and stabilize the tree.
Roots are biologically made to be underground in a dark and moist environment to collect water and nutrients for the tree. Tree trunks are not. The living tissue on trunks can often rot if they are buried for an extended period of time.
Trees that are buried too deep put off adventitious roots on both the trunk and main anchoring roots (buttress roots). Adventitious just means “formed in an unusual or irregular place.” Small feeder roots form on the very tips of the main roots to collect water and nutrients for the tree. These smaller roots will often form around the stem of the tree as a response to being buried too deep. They pose a problem because these small roots grow larger and can begin to cut into or girdle the buttress roots and trunk of the tree over time.
Girdling roots often form on trees that have been planted too deep. Especially those that are in raised planters or stone rings. Circling roots are roots as the name suggests, grow in circles instead of away from the trunk. Girdling roots are roots that have begun to choke the tree because it has grown to close to the trunk. Over time, both the circling roots and trunk grow larger in diameter. Circling roots then become girdling roots as they come into contact with each other effectively cutting off circulation of water and nutrients to the rest of the tree. This is why trees that are planted too deep often show signs of stress.
What can be done?
Expose that flare! This can often be done by hand by gently digging around the base of the tree until you see a taper. Prune off any small adventitious roots or girdling roots with hand pruners or a wood chisel. If your tree is planted WAY too deep or the project is more than you want to deal with, you can have an arborist expose the flare and prune problem roots with an air spade for a very gentle, nondestructive approach to your planting problem.
In future planting situations, apply your new tree root knowledge.
– Make sure the tree is planted at the right depth.
– Make sure the flare is clearly visible and that there are no smaller roots impeding on the main buttress roots in any way.
– Prune or tease any roots that have begun to circle around the tree in the pot so that the roots grow out and away from the tree.
– Stake the tree if it seems unstable. Otherwise, let the tree freely form that natural stabilizing taper.