Fabric weed barriers have greatly improved survivability in new windbreak plantings, especially in the more arid Plains and Mountain states. Millions of trees in thousands of windbreaks are alive today because of these fabric mulches. However, there is a downside.
When fabric weed barriers began to be commonly used in the late 1980s, it was thought that ultraviolet light from the sun would break them down over the first few years after the planting, so they would not girdle the trees as they grow larger. Time has proven this assumption wrong, and because the slits cut into the fabric for those little seedlings were quite small, trunk girdling can actually kill windbreak trees as they grow older.
You might think that the solution for this problem is simple. Just go out in the windbreak and cut the holes in the fabric larger to accommodate tree growth. But it isn't as simple or easy as it sounds. "The full usefulness with the fabric relies on proper installation and follow-up management of the material on-site by the landowner," says Nebraska Forest Service northeast district forester, Steve Rasmussen. "It is especially a problem with the fabric if it is not properly installed and only had a slit or small opening made when the fabric was laid over the newly planted trees or if the fabric gets covered with soil."
Fabric should be laid flat on the ground during installation without a furrow in the tree row that holds the fabric off the ground, making it easy for hot air and rodents to get under it, Rasmussen explains. The fabric needs to be pinned down with a steel pin or large staple within 12 inches of the seedling, to help direct water running on the fabric toward the seedling, not away from it.
Slits in the fabric where the tree is pulled through need to be cut in an X, not as a single slit, so the fabric doesn't rub on the seedling. "Don't cut large holes around the seedling, because that only allows the soil to dry out and weeds to grow around the tree, reducing the effectiveness of the fabric," Rasmussen says.
For landowners with older windbreaks installed with fabric mulch, there are two choices to avoid the girdling issue. Rasmussen suggests using a sturdy hook-ended cutting knife, preferably with a long handle to save on backaches, to cut the fabric away from the trees. The cuts should be made in as many directions away from the tree as you can reach. The second choice is to remove the weed barrier altogether.
When to remove fabric
No matter which method a landowner picks, Rasmussen says that timing is everything. It is easiest to cut fabric away from the trees by hand about five years after planting, depending on the growth of the trees. In older windbreaks where soil has been deposited on the fabric and trees are overgrown, it is best to completely remove the fabric within 10 to 12 years after installation.
CUT IT OUT: At a recent field day near Lynch, Neb., Steve Rasmussen, Nebraska Forest Service district forester, demonstrated several tools available, including this hook-ended knife, which can be used to cut wider openings for trees in fabric mulch or to remove it altogether.
Two years ago, a Brookings, S.D., inventor developed a skid-steer attachment that could rip fabric barrier away from the trees and roll it into a bundle that could be disposed of more easily. Dustin Gibbons, the inventor who founded Duty Metalworks Inc., says that it takes a heavy spindle, 5 or 6 feet long on his attachment, to roll the fabric. Once the spindle is full, the bundle can be lowered to the ground or onto a trailer for removal.
At a recent demonstration of this device near Lynch, Neb., Gibbon's attachment performed well under tough conditions in an older windbreak. The process was still plenty of work, because soil and grass deposited on the fabric over the years made the fabric break during removal. It worked better when the fabric was cut along the tree line ahead of time. Although the fabric would still break at times during removal, it was simply tied back together to continue the operation.
If you would like to learn more about all of the tools and management practices being tested with fabric weed barriers, contact Rasmussen at 402-375-0101.