Mulch protects your trees from soil moisture loss and weed growth while improving tree health and improving appearance. Synthetic tree mulches, whether made from fabric, plastic or rubber, do not decay, so therefore do not improve soil. But the protection they offer to your trees is reason enough to consider their installation.
Landscape fabrics, also known as geotextile material, allow water to pass freely and offer excellent weed suppression. But they are not attractive. In a nursery setting, the fabric allows tree seedlings to thrive without weed competition. But in a landscape setting, the fabric needs a topcoat of bark or gravel. There are different grades of fabric that offer a range of useful lifespans, but five to 10 years is typical.
Plastic is often used in vegetable gardens but its use as synthetic tree mulch is limited. Plastic suppresses weeds but it is not water permeable. Plastic mulch is a helpful weed killer, blocking light and moisture while raising soil temperatures. It can be used as a temporary mulch to kill persistent weeds around trees without the danger of root damage because of chemicals or cultivating.
Shredded rubber mulches gained popularity as a playground cushioning material but are now being used as landscape mulch. Attractive and long lasting, shredded rubber mulch is available in several colors and looks surprisingly like shredded bark or root mulch. A test conducted by the Colorado State Cooperative Extension showed that rubber mulch raised soil temperatures more than traditional wood or bark mulches, but the temperatures were still in a range safe for trees and plants.
Mulch is usually thought of as a weed barrier and moisture retainer, but it offers other benefits as well. When used properly, synthetic tree mulches protect the root zones of trees from temperature extremes. They also prevent erosion and reduce soil compaction while minimizing the need for toxic herbicides. When weeds and grass are kept to a minimum, trees are less subject to damage by weed trimmers.
Landscape fabrics should be laid in a single layer. Use ground staples to secure the corners and edges. Allow at least 2 inches of space around the trunk of the tree to allow for growth. Top with 2 to 3 inches of decorative mulch.
Plastic mulch is not installed permanently. It can be stapled in place to kill weeds. Do not cover plastic mulch---you may forget to remove it and it will limit your tree's water and oxygen supply.
Rubber mulch should be spread to a depth of no more than 2 to 3 inches. Depths greater than 4 inches can restrict water and oxygen flow to the root zone. Spread the mulch in a 4- to 6-foot ring around your tree.