Which mulch is best, and why should you use it?

Not all mulches are created equal. We take a look at the different types and which you should choose for your next landscaping project
Published
2 March 2020
Division
Materials

The benefits of mulch

Mulching is the simplest and lowest cost action you can do to improve your landscape.  Mulching has many benefits and is sourced from a variety of materials.  In this article we explore the benefits of mulching, and the sources and relative merits of mulch products.

Playground mulch

Playground mulches have a specific function of protecting children from falls, and their specification, sourcing and installation is covered by details, standards and regulations as discussed here.

Why should you mulch?

Garden mulch is a layer of material applied over soil in your garden.  Mulching gardens serves several purposes, including:

  • acting as an insulation layer
  • moderating soil temperatures, and
  • improving the look of your garden.

Plants are supported by a network of roots throughout the soil profile. Roots grow best when they are not exposed to extreme hot or cold temperatures, and when the temperature range across the day is uniform.  By acting as an insulation layer, soil temperatures will remain higher during the cool of the night and cooler during the hottest part of the day.  Plants will flourish in this environment as they will not be shocked by temperature changes.

Mulch helps trap moisture in the soil

The mulch layer also traps moisture keeping the top layer moist and reducing water loss via evaporation, this has the benefit of reducing irrigation demands.  Moist soil profiles also have increased infiltration rates as the profile does not need to become saturated. Mulch also prevents erosion of rain by reducing the impact energy of rainfall and trapping and storing rainfall briefly in the mulch profile.

Mulch improves the aesthetic of your landscape

The final benefit of mulch is the aesthetic impact it provides.  Designers can choose from a range of textures and colours, which will be prominent when the garden is established and plants are small.  If the does not contain a ground layer planting the mulch will remain a feature of the garden over its life.  Mulch has the benefit that is can be topped up to keep the garden looking fresh.

Where does mulch come from?

Mulch is sourced from either recycled timber, forestry residues or tree lopping.  Recycled waste comes from pallets, old timber fences, industrial timber offcuts and building demolition.  Good quality mulches can be made from the first three sources, provided waste contamination is managed.  Demolition material makes poor quality mulch, as it is often contaminated with metals and other building materials.  Recycled timber has the advantage that the timber is aged, dry and will breakdown slowly in your garden.  To create mulch the timber is ground in a hammer mill, has any nails removed with magnets and is screened to remove very fine and very coarse particles.

Forestry industries produce by products from hard wood and soft wood operations that are used as mulch.  These products are produced at the mill and it is usually uneconomic to collect forestry residue from plantations.  From pine forests we source pine chips, pine peelings and bark.  Chips are lower grade products that are usually exported for paper production.  Peelings and bark are made when the trees are stripped of their outer covering prior to processing.  Hardwood timber produce chips.

Tree loppers produce mulch when they prune or fell trees and process them by either grinding or chipping the timber.  Tree loppers mulch, also known as bush mulch, varies significantly in quality depending on the trees being chipped and how old the mulch is.  If it is sold green, the mulch will compost in your landscape and may breakdown very quickly, as it is a combination of woody and leaf matter.  Good bush mulch should be aged for at least 8 weeks in controlled circumstances to allow the initial breakdown of material to occur.  It is usually sold as a bulk, unscreened, low cost product.  Mulch from large scale tree clearings, where the material is ground, is usually only suitable for large scale landscapes as it tends to be course and can be contaminated with soil.

Coloured mulches are pine of recycled timber chips that have been “painted”.  These mulches were developed to provide alternatives to red gum and to improve the aesthetics of chips.  They can be supplied in any colour of the rainbow, but are usually in earth hues of red, brown or black.  The colours should stay fast and last at least a decade.

We are often asked “what is the best mulch?”, or “what is the most sustainable?”

Around Australia the ranges of organic mulch varies, reflecting the different timber resources and historical practices.  Therefore, specifications need to adapt to reflect what is available in your market.  Mulch for your project will very much be about what are we trying to achieve with the landscape and what your budget is.  In high visitation areas, you are likely to consider coloured chips or pine barks as they are visually appealing.  If your landscape is very large or will be experienced from a distance, you can consider plain recycled timbers or pine chips, as your decision will more than likely be driven by cost.

All commercial timber mulches are a by product of some other timber production or landscape process.  All timber mulches come from renewable resources and have been diverted from the waste stream and therefore score well for sustainability.  Within the different timber mulch products, cost is a reasonably accurate reflection of the effort (diesel fuel) associated with processing and transporting the material from where it was sourced.  In Melbourne, pine products are the most expensive mulches, because they are the by product of a timber harvesting activities in forest hundreds of kilometres away.  Pine prices in Adelaide are much lower as pine plantations are nearby.

The takeaway from this is price is not a good guide to quality, and higher priced mulches will tend to come with more transport miles and processing. Ecodynamics Mulch products are all classified in our brochure according to their sustainability and their cost, which you can view by clicking HERE. 

 

The best mulch for your project will very much be about what you are trying to achieve with the landscape, and what your budget is

Waste timber from construction activity is diverted from landfill and turned into recycled mulches