All About Mulch

Organic mulches serve several important functions in gardens and landscape plantings.  Mulches help control annual weeds, conserve soil moisture, moderate soil temperatures, and much more.  These many benefits make the use of mulch very beneficial in a wide range of garden settings.  Consider availability, cost, appearance, function, and durability when choosing which organic mulch to use.

Access more in-depth information about mulch types and how to best use mulch in the landscape in this article: Using Mulch in the Garden

Types of Organic Mulches

There are several types of organic mulches available to home gardeners.  Each has advantages and limitations.wood chips and shredded bark as mulch around a tree  Choose the best mulch based on the longevity of the mulch, plants grown in the area, price, and aesthetics.  Organic mulches to consider in the landscape include:

  • Bark - Use bark mulches around trees, shrubs, roses, and in perennial beds.
  • Wood Chips (chipped or shredded, natural or dyed) - Wood chips are best used in landscape plantings, such as around trees, shrubs, and roses, and in perennial beds.
  • Leaves (shredded or composted) - Shredded or composted leaves are an excellent mulch for vegetable gardens, annual flower beds, raspberry plantings, and around perennials, trees, and shrubs.  Leaves are a poor winter mulch for strawberries and herbaceous perennials because they tend to mat down and smother plants.
  • Grass Clippings - Grass clippings decompose quickly, making them great to use in vegetable gardens or annual flower beds.
  • Straw - Straw is an excellent mulch for the vegetable garden and strawberry bed.  It is an ideal mulch for overwinter protection of perennials, roses, and other tender plants.
  • Newspaper and Cardboard - Use newspaper and cardboard as a mulch in vegetable gardens, garden pathways, and around trees and shrubs.
  • Cocoa Bean Shells (also called coco hulls) - Cocoa bean shells are excellent mulches for annuals, large containers, perennials, vegetable gardens, and roses.
  • Pine Needles (also called pine straw) - Use pine needles around trees and shrubs and perennials.
  • Sawdust - Use sawdust in vegetable gardens, perennials plantings, or around trees and shrubs.
  • Compost and Leaf Mold - Compost and leaf mold can be used in nearly all garden settings, including perennial and annual beds, vegetable gardens, and around trees and shrubs.

Mulch Depth

The optimal depth of mulch will vary depending on soil texture, climate, type of mulch, age of plants, and management objectives.  In most cases, a layer 2 to 4 inches thick works well.  Mulch can be applied under the drip line of mature trees to a greater depth than in a bed containing annual and perennial herbaceous plants.

A thin layer of mulch does not suppress weeds or conserve moisture as effectively as a deeper layer.  A thin layer also needs to be replenished more often, which increases maintenance costs.

On the other hand, an excessively deep mulch layer can promote waterlogging of heavy soils, decrease soil oxygen levels, result in shallow rooting, and keep soils too warm during winter.

Inorganic Mulches

Inorganic mulches, like rock and plastic sheeting, can be used but have limitations.

Common inorganic mulches include

  • river rock
  • lava rock
  • pea gravel
  • crushed brick
  • limestone gravel
  • caramel rock
  • rubber chips
  • woven landscape fabric
  • plastic sheeting

Inorganic mulches do not contribute to building soil fertility or composition.  Most will help warm soils quickly in the spring and keep them warmer in the fall but may keep soils too warm in the summer months.  These mulches can be effective at weed suppression, but organic material and soil will build up on top of them over time, leading to weed issues.  They are typically difficult to garden in, making planting and transplanting challenging.  Some inorganic mulches like plastic sheeting will prevent water infiltration.

Additional Information

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