Mulching Tips

Mulch Reduces Stress to Trees
By James Gudenkauf – Outdoor Visions

Mulch is a material used to reduce environmental stress to trees by providing a cooler environment in the summer and warmth in the winter months.  It also helps contain more moisture in the soil for the roots and reduces water evaporation caused by wind and hot sun, which translates into less watering.

It reduces competition of weeds and also prevents damage to the tree by lawnmowers or weed-eaters.  Finally, mulch emulates the tree’s natural habitat by increasing the soil microbial activity and loosening the soil, which can reduce the need for aeration and fertilization.

Mountains of mulch around the trunk can harm trees.  If a little mulch is beneficial for tree health, then a mountain – carefully sculpted against the trunk must be very beneficial, right?  Wrong!!  Never pile mulch more than four inches high.  Care should be taken to avoid over-mulching and not to cover the actual trunk of the tree.

Excessive mulch can smother the tree’s root system and serve as a conduit for harmful insects and disease.  A mulch-free area, one to two inches wide at the base, is sufficient to avoid moist bark condition and prevent trunk decay.

To be most effective in all of these functions, mulch should be placed two to four inches deep and spread over the entire root system, which may be as far as two to three times the diameter of the branch spread of the tree or at least cover as much of the area under the drip line of the tree as possible.

Black plastic is sometimes used to discourage weeds, though it interferes with the normal oxygen and water supply to the tree’s roots.  Plastic barriers can contribute to the creation of a very shallow root system which, during drought periods, makes plants less capable of obtaining water or withstanding heat stress.  There are, however, several landscape fabric mulch products available that will function in the same way as plastic but allow for normal water and oxygen exchange.

Thicker mulch layers, five to six inches or greater, may also inhibit normal oxygen and water supply to the tree’s roots.

Mulch can be applied just about any time of the year when trees and shrubs are being planted.

The best time to apply mulch is in mid-spring, when soil temperature has warmed up enough for sufficient root growth.  If applied earlier, the mulch could lower soil temperature and delay root growth.

In addition, properly mulching your trees assures healthy root growth and prevents damage to the trunk, proper pruning – not topping – is also necessary to maintain or improve the health, appearance and safety of your trees.