When plants are dug in the nursery, burlap is tightly pinned, sewn, or tied around the soil ball so the ball doesn’t fall apart during handling. For large trees, this soil ball may be placed in a wire basket for added protection. If the tree is going to be above ground for awhile, some nurseries will wrap plastic (imagine a giant roll of saran wrap) around the soil ball to help keep it from drying out.
Years ago we did a project to spruce up the entrance to an industrial park. Part of the project was to spade-edge around some existing trees that had been planted a few years earlier, and add new mulch to the beds and tree rings. Our crew discovered plastic buried just below the thin layer of existing mulch. Undertaking a little forensic landscaping, we excavated around one of the trees and found that it (as well as all the other trees) had been planted WITH THE PLASTIC STILL WRAPPED AROUND THE SOIL BALLS.
Some plastic degrades above ground when exposed to sunlight. How long that takes depends on the type of plastic. But, plastic does not decompose underground, at least in the time scale of a human life, or even the much longer lifespan of a tree. And some plastic doesn’t seem to degrade, even in sunlight.
My great-great-great grandchildren could go back to this project, dig in the ground (the trees would be long dead and gone – having been cut down after a period of inexplicable poor and declining health) and find this plastic intact.
The practical advice:
All plastic, including plastic twine, should be removed after the plant is placed in the hole, just before backfilling.
If there is a wire basket, at least the top half should be removed after the tree is maneuvered into the hole. It’s easy to do with a bolt cutter.
The burlap should be cut off the sides and top of the soil ball. This is NOT easy to do because the human body is not built for kneeling on the ground, leaning over a hole, and working with 2 hands deep in the hole, often with minimal clearance underneath low branches. A third arm sure would come in handy here. You can lie flat on your stomach, which may hurt your pride, but save your back.
