By DIANNE WALKER | Special to The Sun
Mulching is one of the best methods for maintaining the health of trees and shrubs. It retains moisture around plant material and protects from injury by equipment. It also maintains stable soil temperature and smothers weed growth. Additionally, mulching provides plants with nutrients through decay of the mulch material and is aesthetically pleasing.
In recent years, however, the standard practices for mulching is rising at an alarming rate and truly defeating its beneficial intent. I see so many landscapes scenarios, from individual trees and new installations to commercial landscapes literally buried in mulch! Hopefully, a few facts and some proper mulching practices will encourage the return of sensible industry standards and save everyone a few bucks in the process.
Getting the most from your mulch
A good rule of thumb is to make sure you are starting at the right depth for new plantings before you apply mulch. Shallow rooted shrubs, such as rhododendron and azalea, are prone to suffocate if too much soil and mulch is piled on top. If possible, create a bed of at least 12 inches beyond the root ball for newly planted trees and shrubs and out to the drip line of established trees. Finally, when you are ready to lay the mulch, do not apply more than two to four inches above proper soil level!
Regardless of mulch type, either organic, (wood chip, pine needles, shredded bark, leaves) or inorganic (rocks, pebbles, black plastic, landscape fabrics) keep the mulch at least three to six inches away from the trunk of young trees and shrubs and at least eight to 12 inches away from mature trees.
What can you do about an established mulch volcano?
Remove excess mulch using a shovel, trowel or whiskbroom while taking care not to injure the trunk. Your goal is to try to remove mulch to the proper depth without harming the bark or the root system. The outer bark is thin at the root collar and can be damaged easily.
Over time, fine roots may have started to grow in the mulched area. In this case, you may have to remove the mulch in stages. A hard stream of water may be used to remove excess mulch and soil from the trunk and flare. Cut off secondary roots that may have grown into the mulch. Trunk and flare should be visible. New mulch can then be applied to the proper depth and distance from trunk.
Everyone needs to take responsibility. If you hire professional landscapers, please make it clear in your annual maintenance you want mulch only two to four inches around shrubs and trees and in all your planting beds. Additions should be made only to maintain proper depth. Fluffing the old mulch before adding more will prevent it from forming a hard surface that deflects water rather than retaining it.
Fine textured mulches, such as double shredded bark or buckwheat hulls should be applied two to three inches deep, while courser mulch products like wood chip can be piled to about four inches. Consider what you already have in place. Removing old mulch is not necessary as it defeats one of the purposes of mulch, which is to decay and mix with the soil. Unless it has become compacted or is full of mold or weed seeds removal is not necessary.
Having the old mulch cultivate (raked through with a three pronged tool) can sometimes be sufficient in the alternate years. As we learn and take better care of our landscape — especially our trees, they will surely take care of us with years of protection from the sun, providing clean air to breath and a welcomed spot to rest our weary souls.
Diane Walker is a member of the Moorestown Tree Planting and Preservation Committee.