It just dawned on me that I haven’t written yet about something that I’ve seen more and more — on virtually all my projects for the last several years, in fact — with new trees being planted in the landscape. It’s this:
Trees coming in from the growers these days (at least here on the East Coast) are often burlapped too deep to begin with. Cultivation practices in the growing nurseries have changed in the last several years; when tilling machinery runs up and down the rows, they flip loose soil toward the young trees’ bases, where it piles against their trunks. The soil is not raked or pulled away, unfortunately, and accumulates with each pass of the cultivating machinery.
When the trees are dug, they are burlapped and basketed to make handling easier, and the picking up and moving of the trees can squnch soil even more snugly around the trunks. By the time a tree reaches its site, it may have 4-8″ of soil above its root flare. If it has been in the nursery long enough, it may have started to grow a secondary root system into the extra soil; the root flare needs oxygen, and feeder roots that are too deep stress a tree.
It’s really important, in the planting process, to check the root flare and see that it is in the proper relation to actual finish grade, and if it isn’t, to pull away (gently, please — that bark may be tender!) the extra soil and expose the root flare. If that new little wiry root system has started to grow, it can be cleanly cut away at this point.
These days, I see lots of trees planted too deeply. I figure that it’s because the contractor assumes that the top of the root ball is the actual finish grade required by a tree. A stressed or ailing tree may sometimes be saved by the simple act of excavating that extra soil, and letting the root flare breathe. (When a young tree has been in the ground on site for a year or more and isn’t settling in well — has small leaves, looks chlorotic, has sparse foliage — the first thing to check is the root flare relationship to finish grade.)
Arborists know about this problem; they’re often called to a site to find out why one or more new trees is doing poorly, and often they find that correcting the soil depth takes care of the issue. Some contractors know about this problem, but typically their laborers don’t, and it takes time and focus to teach them and have them make the correction with every tree. The landscape architect’s insistence on excavating that root flare can make the difference between a tree that settles in and thrives and one that struggles and develops more problems.
Ideally we could team with arborists, with nurseries, and with other landscape architects to get word to the growers that changes to their cultivation practices could eliminate the problem of trees showing up on site buried. In the meantime, making contractors aware of the issue — and being sure they address it during planting — can help insure the good health of our tree plantings, and the integrity of our designs.