If you don’t think volcanoes are abundant in northeastern Illinois, take a look at this “mulch volcano.”
A mulch volcano is the name given to the improper mulching technique used by many landscapers and homeowners. A mulch volcano is a large pile of mulch often too deep but also incorrectly piled against the stem or trunk of a tree or other type of plant. Mulch touching the bark or stem of plants leads to rot, pests or diseases over time since mulch retains moisture. Also, when mulch is applied too deeply, it can prevent water from infiltrating down to the soil, causing some roots to grow up through the mulch in search of moisture, which is not where roots should grow.
It is recommended by most tree and plant experts to keep mulch 3-4 inches away from touching tree trunks or shrub stems, and 1-2 inches away from perennials or annual stems, often referred as a “mulch donut”. Also, mulch should only be applied 3-4” deep around trees or shrubs, and 1-2” deep around perennials. If I am mulching a large area, I typically spread the mulch first, then go back and with a small shovel, rake or gloved hands, and pull the mulch away from stems or trunks.
Organic mulch (wood, leaves, straw, etc.) helps keep the ground moist, reduces weeds, adds organic matter, and prevents lawn mowers and other yard equipment from damaging trunks or stems, if applied properly. Bark mulch is popular, but I suggest also using leaves or decomposed leaves otherwise know as leaf mold around shrubs, trees or woodland perennials. This is how nature mulches, it saves on many types of costs (energy, transportation, time, noise pollution…) and adds organic matter to soils. Leaves also provide food, nesting material, and cover for several types of wildlife, including birds and butterflies.
No one rakes the leaves at the Maple Grove Forest Preserve in Downers Grove, or at most other area preserves. The native plants and wildlife benefit.
No one rakes the leaves in a woodland. The native plants and wildlife benefit.
According to a Wild Ones lecture I heard from a professor from the University of Madison, growing native groundcovers, wildflowers, grasses, sedges, ferns compatible with or found naturally growing under our native trees and shrubs is even better than just mulch alone. Native plants naturally grow under trees and shrubs in a healthy ecosystem, so it make sense, doesn’t it? If you cannot grow plants underneath, organic mulch is the next best thing to apply around native trees and shrubs, or any trees or shrubs, over lawn or non-organic mulch. Lawns provide too much competition for resources, some lawn chemicals can harm trees and lawn equipment can damage tree trunks or roots.
If you have a large tree, make sure the outside diameter of the mulch donut is at least 6-8 feet wide or even larger, if space allows. See photo of this huge oak and mulch ring found at Herrick Lake. If this oak could talk, it would say “Ahhhh. If I can’t have native plants on the ground around me, this large organic mulch ring is sooo much better than lawn!” Don’t forget to leave some bare areas of soil for our native ground nesting bees, which need our help too!
Let’s leave the volcanoes where they naturally occur, and mulch out, not up.
By Denise Sandoval, Conservation@Home Assistant
Additional Resources:
Ground nesting bees: http://greatpollinatorproject.org/management/nesting-habitat
Leave Leaves Alone: http://www.leaveleavesalone.org