It’s March, and that means it’s time to freshen up the mulch in planting beds and especially around trees. Mulch – when properly applied – has many benefits for trees and other landscape plants. Among those listed in the 2010 International Society of Arboriculture (ISA) Arborist Study Guide are:
- Moderation of temperature extremes;
- Reduction of competition from weeds and grasses;
- Protection of trees from mowers;
- Maintenance of soil moisture; and
- It looks good!
The ISA lists mulching as a water conservation technique, stating that mulch improves soil structure, reduces soil moisture evaporation and mitigates soil compaction and erosion. According to the ISA, organic mulches help increase organic matter in the soil as they decompose, enhancing soil biology, fertility and structure (p. 60.)
To maximize the benefits of mulch – and avoid actually harming trees – it is critical to employ proper mulching techniques. The Virginia Cooperative Extension publication Mulching for a Healthy Landscape offers great guidelines on how to mulch:
“For trees and shrubs, spread mulch evenly to a depth of 2 to 3 inches. For trees and shrubs in beds, mulch the entire bed. For those in a lawn, mulch a wide ring (extending from 3 to 6 feet out from the trunk) around each plant. Never pile mulch against tree trunks. Pull mulch back away from the trunk about an inch or so. As organic mulches decompose, they may need to be replenished somewhat every year; but don’t let mulch build up to depths greater than about 4 inches.”
Loudoun County Master Gardeners cautions against over mulching in its publication Mulch Out Not Up. According to the publication, symptoms of over mulching sometimes take 3-5 years to show and include: discolored or abnormally small leaves, poor twig growth and die back of older branches as well as rotting or pealing bark under the mulch.
Any time this month is perfect for mulching, but this year sooner is definitely better. That’s because weeds are already popping up in the wake of the warm winter. Mulching now will help control those weeds and make bed preparation easier than it will be once the weeds start to take over. Blake Landscapes adds a pre-emergent herbicide to planting beds just before mulch is applied, helping to reduce weed pressure throughout the season.