Arbor Advice: Why mulch is critical to tree careMarch 28, 2017
Mulch protects, retains moisture and reduces competition
Unmulched trees often have grass growing right up to their trunks, which puts them at risk of injuries from lawn equipment.
Spring is just around the corner, and even though it’s a bit too early for many of us to get outside, it’s not too early to start planning. So while you’re putting together your to-do list, think about putting mulch around your trees to optimize their health.
Arbor Advice is written by the International Society of Arboriculture
for Redefy Real Estate
Mulching looks great, but it’s much more than cosmetic—in fact, it’s one of the most beneficial practices you can use as a homeowner for better tree health. In addition to improving appearance, mulch provides a number of benefits:
- Helps retain soil moisture
- Helps reduce competition from weeds and grass
- Increase soil biology and fertility as it decomposes
- Protects the trunk from serious injuries caused by lawn care equipment
Organic mulches (such as wood chips, pine needles, bark, or leaves) are typically preferred because they provide greater benefits. Inorganic mulches (such as various types of stone, lava rock, or pulverized rubber) can be a better choice if high wind or flooding is an issue, or in places where fire resistance is particularly important.
Before putting down any mulch, remove weeds and grass from the area using your hands or a hand tool—avoid mechanical equipment that can damage the tree’s roots or trunk.
Before mulching, remove turf and weeds by hand or with a small hand tool.
The mulch you put down should only be 2 to 4 inches deep, and should cover as much of the root zone as possible—ideally from near the trunk to the dripline (the edge of the tree’s canopy). It’s often applied too deep and in too small a circle around the trunk, which offers little benefit to tree roots.
Apply mulching materials 2-4 inches deep while avoiding the trunk flare. Don’t cover exposed roots.
Follow these tips to optimize mulch and its benefit to the tree.
- Leave a space of about 4 inches between the mulch and the trunk. Mulching against tree trunks can retain moisture and provide an environment for the growth of fungi.
- Don’t bury the trunk flare (the trunk flare is the place where the trunk expands at the base of the tree).
- If you are mulching trees that are in close proximity to one another, consider mulching in a continuous bed rather than as individual rings.
- A broad circle of mulch is desirable, but if you are mulching larger, existing trees and can’t mulch the entire drip line, make your mulch circle at least 3 times the trunk diameter.
- Do not use plastic or fabric sheeting under mulch. It will stop water movement into the soil, limit incorporation of organic matter, and may result in oxygen restricted conditions in the soil.
- Resist the urge to put down too much! Mulch that is too deep can limit soil oxygen levels and may provide habitats for small mammals that can girdle stems.
Mulching will give your landscape a clean, manicured look. It will weather over time but will continue to benefit your trees.
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