It’s that time of year – the weather has warmed and the risk of frost is gone. You or your landscaper may be planning to spend some time mulching flower beds and trees in your yard. Mulching around trees can be a helpful practice, and it creates a neat, orderly aesthetic. It keeps mowers and weed wackers at bay, and prevents grasses from encroaching on the tree and competing for water.
Mulch is chipped or shredded wood which serves to regulate temperature and retain moisture, and deposits nutrients into the soil as it decays. It is especially helpful for young plants and trees as it protects roots from freezing, enhances the soil profile, and prevents weeds and grasses from establishing themselves at the base of the tree.
A word of CAUTION: Beware over-mulching around trees (known in the industry as “mulch volcanoes”. It’s a common mistake and can easily kill the tree!
What can happen to trees under a Mulch Volcano?
- Cankers. The bark at the base of the trunk becomes saturated as it is permanently shaded and enveloped by moist mulch. This can result in cankers, which are dead sections, or wounds in the bark on branches. These become especially vulnerable points to fungi and bacteria. Bark is the protective layer around trees, and is designed to prevent disease and insects from penetrating the tree. It requires free flow of air, sunlight and a dry environment to stay hardened and functional.
- Disease / Decay. Over-mulching creates a wet, dark and warm environment which promotes growth of fungi and bacteria on the trunk and roots.
- Insect and Rodent Infestation. Rodents, like voles and moles, along with infectious insects are attracted to the free meals available in rotting wood.
- Root Rot. Trapping moisture at the base of the tree will result in oversaturating the roots and cause the roots to begin to rot.
Any and all of these conditions will ultimately result in the slow death of the tree, or even cause it to fall suddenly. This isn’t how you want to see your expensive landscape feature perish!
How to properly mulch a tree:
Spread an even layer of mulch around the base of the tree at a depth of 2 inches to 4 inches. Do not exceed 4 inches in depth of mulch. We recommend organic or clean mulch that is free of any contaminants, chemicals, or shredded inorganic debris. You can refresh the mulch twice a year, in spring and fall are ideal times.
If you’d like, you can add fertilizer to the tree when you place the mulch. Placing it on top of the mulch will allow it to dissolve and infiltrate the soil beneath. If you want to add compost, add this to the soil when you plant the tree. If you do want to add compost to an already established tree, place it in a thin layer beneath the mulch, and count the depth of the compost layer toward your total mulch depth.