By Colleen McKenna
with Chris Chantler (Photo)

What is mulch? Basically, it is a material that is used to cover the soil in garden beds to retain soil moisture, prevent soil erosion, and cut down on the weeds.

That brings us to the big question: what mulch is right for me? Here is a list of mulches with their advantages and disadvantages.

Common Mulches:

Leaves:

  • use ~ 10 cm (4″)
  • free
  • need to wait for fall for your supply
  • can blow away in wind
  • will break down quickly
  • adds nutrients to the soil
  • best if used dried and crumbled

Grass clippings:

  • use ~ 5 cm (2″)
  • free and constant supply from mowing
  • must be added in thin layers over time or it will tie up nitrogen in the soil
  • adds nutrients to the soil
  • can only be used if weed seed free and not chemically treated

Gravel, stones, rocks:

  • use ~ 5 cm (2″)
  • expensive (sold by weight)
  • usually used with landscape fabric underneath
  • permanent
  • can be difficult to add new plants to a bed
  • needs to be kept clean or material will break down into humus and weeds will grow
  • adds no nutrients to the soil

Wood, bark chips:

  • use ~ 5 cm (2″)
  • free if obtained from arborist company
  • commercial products can come in variety of colors
  • adds nutrients to the soil
  • needs to be replenished (time depends on size and type of wood)

Groundcovers:

  • can be a cost depending on source (ie. From neighbour – free vs. nursery – cost)
  • variety of choices depending on the location needed (sun or shade)
  • usually takes nutrients from the soil as it grows

Newspaper:

  • use ~ 0.5 cm (0.2″)
  • easy to obtain for free from neighbours
  • non-glossy type must be used only, other types will add toxins to your soil
  • must secured down (ie. rocks, soil, grass clippings, etc.) or will blow away in the wind

Coffee grounds:

  • use ~ 5 cm (2″)
  • can be easily obtained from coffee shops
  • has a nice smell
  • adds nutrients to the soil

Compost:

  • use ~ 7.5 cm (3″)
  • can be purchased or made in your yard
  • adds nutrients to the soil

Coir:

  • use ~ 5 cm (2″)
  • lasts 2 years, according to the manufacturers
  • takes time to hydrate before use (~30 min)
  • more environmentally friendly than peat moss

NOTES:

  1. I have heard concerns about using cedar mulch because it is acidic. However, through my experience, I don’t know anyone who has had problem with growing plants. So, I would advise you to use it if that is what you prefer.
  2. I have read and heard not to pile mulch near the crown of plants. I don’t follow this reasoning. In nature, mulch is not carefully placed around plants and they thrive.
  3. I went to a lecture and listened to a potential problem with using landscape fabric. The gardener brought up an interesting case. He had a client with a tree that was doing very poorly. The pores in the fabric had clogged up over time which deprived the tree of oxygen. It had very shallow root growth. When the fabric was removed, the tree finally started to improve.