Mulches

Purpose

Mulches go around the base of a tree or other plants. "mimics" litter layer in a forest.

• Helps retain moisture
• Improves infiltration/reduces runoff
• Reduces competition from weeds
  • Blocks light from below and keeps seeds from germinating or from landing.
• Can create a lovely seed bed.
• Doesn't help as much as people think (probably tons of herbicide being laid down where weeds are not present)
• Creates a visual boundary for trees (helps because people seem to like to mow down saplings)
• Moderates temperatures

 

Concerns

Woodchips have a C/N ratio of 1:400; compost of 1:20; What does this mean?

• A mulch with high C/N ratio can cause nitrogen deficiency, especially if mixed in the soil
• Materials with lots of cellulose tend to have a higher C/N ratio
• The C/N ratio of wood chips will decrease as a mulch is aged
• The fineness of the material and extent of mixing play a large role in the influence of C/N ratio

 

Research shows this isn't usually an issue.

Types

• Aged, shredded hardwood bark
• Woodchips from landfill
• Cypress bark
• Pine bark (shredded and "nuggets")
• Pine straw (slash and longleaf)
• cocoa hulls
• Nut hulls
• Various nonaesthetic types and firehazards