Mulch Matters – A Tiny Success Story
By: Nina Fisher
In the early 2000’s, the Naval Academy enhanced the perimeter of its 80-acre stadium property by installing a meandering 1.25-mile multi-use trail lined with native trees and shrubs. I was ecstatic! I live a few blocks from the stadium and was looking forward to a shady place to walk or run without worries of car traffic.
It seemed like a promising start. Landscapers planted the trees and shrubs, installed raingardens and mulched it all. But like many ambitious projects, it lacked a key element: proper planting and mulching.
My blood pressure rose precipitously as I walked the newly planted area. With knowledge and experience thanks to my educational background and my tenure as a Watershed Steward , I saw far too many problems. The trees were planted way too high; their root balls were sitting well above soil level, and were topped with 8 to 10 inches of mulch piled directly against the tree trunks. It was a recipe for disaster. When trees are planted too high and engulfed with excess mulch, they develop collaring roots that encircle the trunk.
Excess mulch also:
makes trees much more prone to desiccation (when the root ball dries out ultimately causing leaf wilt and drop);
creates an environment prime for rot and disease; and
prevents rainwater from reaching the roots.
I contacted the head of the Naval Academy Athletic Association, and he walked the trail with me. I pointed out the assorted problems and told him that they were going to lose a lot of these trees and shrubs. He agreed with my assessment and vowed to do it right going forward. They didn’t.
Over the years, I estimate that at least a third of the original plantings died, and many others are compromised. Last fall, I walked the path with the new Navy landscape contractor and we talked about planting and mulching practices. They had just planted 35 new 10 – 12-foot trees and I pointed out the poor planting. The next day he had his guys replant all the trees properly. A small victory!
This spring, when the Navy landscapers usually swoop in to pile excessive mulch around the trunks, they didn’t! They distributed a couple of inches of mulch around each tree and none of it touched the trunks. My blood pressure stabilized—another triumph!
Mulch can be an appropriate and attractive top dressing for your garden and tree beds, but the adage of more is better certainly does not apply here. Here are a few tips to keep in mind:
Have you ever noticed that trees have a natural flare just above the soil level. That flare should remain exposed; your tree should not look like a telephone pole planted in the ground.
Spread the mulch outward rather than up. It should extend away from the tree out to the drip line, the area defined by the outermost circumference of a tree canopy where water drips from the tree leaves and onto the ground of the tree.
The mulch layer should be only 2 to 3 inches thick, which is thick enough to suppress some weeds, mitigate temperature swings, leach nutrients slowly into the soil and ultimately add organic matter that will enhance soil quality and health.
Any organic matter can serve as mulch, not just the stuff in bags at the big-box stores. Ground-up leaves, pine fines, shredded barks, wood chips from an arborist’s grinding machine all work.
If you do buy mulch, select a type that is not dyed as the coloring chemicals are unnecessary and can leach into the soil.
One more thing—you could be making mulch ado about nothing! If you have a large, planted area with trees, shrubs and perennials with leaves that are left to degrade in place each fall, you can just leave the bed alone. You’ve created your own little functional ecosystem! After all, no one mulches the forest.
Nina Fisher
Watershed Steward Class 5
WSA Board member and Tree Trooper
Co-founder of Save our Trees
Watershed Steward Annie Hilary, In partnership with the Master Gardeners, has a campaign to stop volcano mulching in our communities. In addition to presentations, Annie has created outreach materials in English and Spanish. Visit aawsa.org/seasons and print the proper mulching flier and share it with your neighbors and local landscapers.