Trimmers Damage Trees
There are several good reasons to keep a mulched area around the base of trees growing in a lawn area. The most important reason is that mowers and line trimmers damage the bark of trees. This can cause stunting and can eventually kill a tree.
The inside area of bark is a living part of the tree. A new layer of bark is produced each year. The inside layers of bark contain tubes which transport food produced by the leaves down to the root system. Without this food, the roots cannot survive.
Line trimmers remove a little bark each time they are used to trim around a tree. With repeated use they can cut entirely through the bark. If part of the tubes are cut, the flow of food to the roots is reduced, causing a reduction in growth. If cut all the way around the trunk, the tree will gradually die in a few weeks.
The second major reason for providing a mulched area around trees is that it increases the growth rate of young trees. A newly planted tree without grass or weeds growing next to the trunk will grow at about twice the rate per year. That will make a significant difference in a few years.
Grass plants have a shallow fibrous root system which is very competitive for water and nutrients. In addition, grass roots produce a growth inhibitor which reduces the growth of nearby plants. The combination of these two factors effectively doubles the growth rate of young trees without grass competition.
Weed and grass free circles around trees can be maintained in several ways in addition to pulling or cultivation. Edging barriers such as bender board, metal or plastic can be placed at the outer edge of circles. Edging prevents grass from growing into the circle. Edging can be moved outward as trees grow larger.
Weed barrier fabric can be placed around the tree trunk and then covered with bark or other mulch. Make sure that the fabric is porous to allow air and water to flow through to the roots. Bark mulch alone will prevent about 90 per cent of weed growth by preventing light from reaching weed seeds. The fabric not only cuts off light but acts as a physical barrier. Eventually weed seeds will blow in on top of any mulch and require some physical weeding or spraying.
Roundup and other brands of weed killer containing glyphosate can be used to kill existing weeds and grass. It will not cause damage if sprayed on the trunk but should not be sprayed on green tissue. Natural citrus oil and potassium salt weed killers can also be used to kill existing weeds.
Casoron and other granular weed preventers will prevent new weed growth. Corn gluten is a natural organic weed preventer.