In three short decades, volcano mulch has become one of the greatest threats to newly planted and young trees and shrubs. If unchecked, the significant monetary and human investment in greenscapes will result in more and more dead and dying trees.
Volcano mulch is the over-mulching of plant material, notably trees and shrubs. Mulch plays an important role in protecting plant material from irreversible lawnmower and weed whacker damage as well as providing for some control over weed competition and soil water retention. Seemingly, rings of mulch have also become landscape design features.
While deadly, the problem is simple; people are placing heaps and heaps of mulch around trees and shrubs and right next to the thin, vulnerable bark. The fact is you do not need more than 2-3 inches of mulch in depth for the desired purposes. Mulch should not come closer than 2-3 inches from the plant. Yet people are piling mulch 6 inches or more, and right on the trunks of the trees, causing damage to life sustaining cambium (the live tissue just below the bark). Beware of volcano mulch in your yard.
UConn Extension has noticed a growing problem in Connecticut landscapes – tree volcanoes. A tree volcano occurs when mulch is piled around the base of the tree and climbs up the trunk. The shape of the mulch resembles a cone or a volcano. Mulch volcanoes waste money and damage trees.
Mulch is useful at the base of a tree for many. When done correctly, the mulch protects the tree from a lawnmower or string trimmer, aids in keeping the soil moist and keeps the ground cooler in the summer and warmer in the winter. Mulch also improves soil structure, aeration and prevents soil erosion and runoff.
Bark is the outermost protective layer or skin of a tree. To properly function, bark needs to be exposed to air. When mulch is piled around the trunk of the tree, the mulch softens the bark and allows outside organisms like varmints, insects, bacteria, virus and fungi to penetrate into the tree. Over time a tree volcano will kill the tree.
Ideally, a mulch ring is placed at the base of the tree immediately after the tree is planted. Follow these steps to correctly apply mulch to the base of your trees:
Before you apply mulch, remove any weeds from around the tree.
The mulch ring should be 2-3 feet wide around the tree trunk radius.
Maximum depth of the mulch is 2-3 inches – the roots need to breathe. Taper the mulch layer to the grass at the edge of the ring.
Aged wood chips or shredded bark are the best choices for mulch.
Mulch shouldn’t touch the bark of the tree.
Trees 10 inches in diameter and larger don’t need mulch.
For more information on tree volcanoes or other home and garden questions, call UConn Extension at 860-486-6271 or visit www.ladybug.uconn.edu