Mulching - Arborist Services


A layer of organic mulch of between 50-100mm (ideally 75mm) provides a wide range of benefits to plants as follows:

  • Reduces moisture loss from the soil
  • Improves soil texture and water holding capacity
  • Improve water infiltration rates
  • Protects the soil and root zones from extremes of temperature
  • Provides a continuous supply of nutrients for plant growth
  • Buffers extremes of soil pH, tending towards neutral
  • Increases microbial and invertebrate activity in the soil
  • Protects the soil against compacting forces
  • Suppresses weed growth
  • Reduces run-off and soil erosion

There are numerous kinds or mulches available. They may be organic or inorganic and comprise a wide variety of materials, particle sizes and properties. An assessment needs to be made of the materials that are available, affordable and provide the right characteristics for the task.

Mulches for use around trees should have the following properties;

  • The mulch should be partially composted (moist storage for a minimum 8-12 weeks in a pile prior to use). Storage and partial decomposition decontaminates the mulch, degrading natural toxins and stabilizing the materials.
  • The material should comprise a majority of particles >15mm. The upper size limit will often be determined by appearance but is usually within 25-75mm depending on application.
  • The fines component of the mulch (leaves, flowers, fruits, bark, wood) should not contain materials that matt or stick together such as lawn clippings, tub-ground bark or wood.
  • Mulches generally will not contain manures, bio-solids, fertilizers or other contaminants.
  • Mulches must be free of weed seeds, disease (particularly Armillaria and Phytophthora spp.) and refuse.
  • The materials should not decompose too fast or be so light that they will blow away.
  • In public environments the appearance of the mulch may be an important consideration.

Mulch must be spread by hand over the root zone, not by machinery driving over the root zone.

Organic mulches degrade over time and so they need to be periodically replenished. The frequency of replenishment depends on the composition of the materials involved but will usually be every 2 years for mulches containing hardwoods and every 12 months for softwood based mulches.

Talk to our qualified and experienced Arborists for advice and a quote on mulching by itself, or as part of a site remediation plan.