Mulch madness: Before you pile it on in garden, learn to avoid the dreaded volcano
March Madness wrapped up a few weeks ago. If you look around, it is now time for mulch madness. Bags of mulch are flying off store shelves in our community’s zest to spruce up landscapes. The concept of spreading mulch seems simple enough, but a few things need to be corrected when mulching.
The purpose of mulch is to cover the soil to conserve moisture, suppress weed growth and reduce grass competition while improving the growth of trees and shrubs. Over time, mulch sources from shredded wood or bark break down, add organic matter to the soil, and feed the plants and microorganisms. It also adds a finishing touch and looks nice.
The mulch depth required to provide these benefits is 2 to 3 inches. This depth allows for water movement and the air exchange needed for root growth. Thinner layers may not provide the benefits, and depths over 4 inches will slow the air exchange and limit root growth.
Estimate the current mulch depth and add to the optimum depth. The goal is to maintain this depth. This does not mean we need to add 2 to 3 inches yearly. Only replenish what has broken down. The existing mulch does not need to be removed.
Mulch should also not be placed or piled against the bases of plants. When mulching, think of donuts and bagels. There should be a hole or ring void of mulch around the base of trees, shrubs and other plants. Keep the mulch 2 to 3 inches away from the bases.
Placing mulch up against the trunk of trees creates a moist area. Constant moisture next to a tree can cause rot and decay of the bark layer of the tree. If the bark rots, this exposes the cambium layer and can lead to the tree’s decline. Piling mulch up on the tree trunk is called volcano mulching and is a bad practice.
The type of mulch used is a personal preference. The plants do not care what is used. They only care if it was applied correctly. All mulches provide the same benefits. Mulch types range from shredded wood and bark to products dyed in various colors. Appearance only matters to you.
The other issue is cost. Mulch can be expensive or low-cost. Much of the cost of mulch is shipping. Several local companies make mulch from waste wood products. Local sources are greener as shipping great distances is not necessary.
Low-cost or free sources of mulch can be available from local arborists. Many tree trimmers will drop a load of chipped wood from pruning for free or a tipping fee. Arborist wood chips provide the same benefits. The only exception is that particle sizes may vary because they have not been screened. Don’t worry about disease or insect transmission as mulch is not a host. Websites such as chip drop (getchipdrop.com) help coordinate the delivery when in your area.
If you are participating in mulch madness, apply correctly and help create a pleasing landscape.
Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Need help? Contact the Johnson County Extension gardening hotline at 913-715-7050 or email garden.help@jocogov.org. The Kansas Garden Guide, your one-stop vegetable resource, has just been updated. Find your copy by going to ksre.k-state.edu and searching Kansas Garden Guide.
This story was originally published April 28, 2023 at 6:00 AM.