Organic Soils and Mulches
Note: We suggest chunky mulch as a groundcover mulch for large and commercial landscapes
By Todd Layt
Way too often landscape professionals use organic soils and mulches incorrectly. It’s unfortunate but the confusion is amplified by suppliers promoting the wrong type of products as ground cover mulch, and inadequately refined products for soil conditioning or soil blends.
Australian trials plus years of real world evidence show us which types of mulch perform. You can achieve outstanding results when you simply use the correct products for the job. There’s no need to worry about it too much, it’s really not that hard, simply follow some basic guidelines when choosing which organics to use in your landscape.
Choosing the right ground cover mulch has one main rule. Only use chunky mulch with preferably zero fines. (See tips below for Roads department specifications). AVOID fines, slivers, forest blends, leaf litter, and raw tub ground mulch from land clearing. All these products are worse for your plants than using no mulch at all. DO USE chips and chunks that have a minimum particle size of 15mm, and avoid any fines. The reasons why this rule is so important are very clear.
Firstly, fine particles act as a seed raising mix. Fine grade organics make the best potting mixes and soil conditioners, which allow seeds to germinate really well. Ground cover mulches’ primary job is to stop weeds. Only chunky mulch types with zero fines do this, as there are lots of air gaps that make it very hard for weeds to germinate, or the depth of 75mm stops weeds from breaking through from the soil below.
Commercial landscapes cannot afford to replace mulch every 1 to 2 years, so slow to break down mulches are required, and only chunky style mulch does this. Good hardwood chunky mulch can last up to 7 years; however a top up may be required after about 4 years in many situations. Good chunky bark products last 2 to 5 years. In Victoria Chunky Bark products seem more popular and seem to last a little longer, maybe due to the cooler weather.
Ground cover mulch is used to improve the health of plants. Only chunky mulch does this, and in fact fine grade mulch used as a ground cover will… read more