Over-Mulching

As beneficial as mulch is, too much can kill trees and shrubs. Michigan landscapes are falling victim to a plague of over-mulching. No more than 2 to 3 inches of mulch should be used. Piling up mulch around the trunk or stem in a mulch volcano will eventually kill the tree. Thick blankets of mulch can become matted and actually prevent water and air from getting to the roots. Follow these key points below for proper tree mulching:

When Mulching At the Time of Tree Planting
  • Dig shallow planting holes 2 to 3 times as wide as the root ball.
  • All wires, tags, and burlap should be removed from the tree.
  • Prune dead or crushed roots with sharp pruning shears to make clean cuts.
  • Only stake trees with large crowns or those situated on windy sites.
  • Backfill holes with existing soil. Compost can be added (if it is well mixed with the soil) to compacted soils.
  • Place compost on top of the ground after planting. Compost contributes beneficial bacteria and helps hold water.
  • Mulch lightly (2 to 3 inches) with aged wood chips.
  • Mulch should be kept away from the base of the tree and spread over the surface to the drip line or crown. Think “mulch donuts” – not “mulch volcanoes.”
After Care
  • Water is crucial for proper tree establishment. If it is hot, 1 inch per week is needed (regardless of the amount of precipitation that is received). If gator bags are used, they should be filled twice per week.
  • Replace mulch each year. Keep grass and weeds out of the mulched area, since they compete with the tree for water and nutrients.
  • Reduce or eliminate herbicide use near tree and in surrounding lawn.
  • To protect the tree trunk, keep lawn mowers and weed chips away from the base of the tree.
  • Fertilizer should only be applied only after the 1st year and only if nutrient deficiencies in the soil have been identified.
For More Information
For more information, contact Michigan State University - Macomb County Extension at 586-469-6430 or Southeastern Oakland County Water Authority at 248-288-5150.