The do’s and don’t of Mulching
DO
- aim for a depth of 10-15cm thick
- water the soil and site well before spreading the mulch
- if using a high carbon-based mulch, such as bark, spread some nitrogen fertiliser over the site first to avoid any ‘nitrogen drawdown’
- replenish the mulch every year, or when the mulch gets to less than half the depth it was originally put on
- ask the supply yard for their Fire Ant Free certificate if they are in a relevant zone (if in QLD)
- when sprinkling, remember that you need to supply enough water to pass through the mulch and to reach the root zone
DON’T
- use stones in areas where there is a lot of leaf fall otherwise you will be forever cleaning the stones
- use plastic as a mulch
- use fine grade mulch on steep slopes otherwise it may wash off in the next heavy rainfall and may cause erosion
- mulch up against the base of a plant or tree – this can weaken the specimen and allow borers and pathogens into the plant/tree
- use fresh pure grass clippings as mulch around plants – it should be allowed to compost down first
- use paper or other cellulose high products in high risk termite zones
- accept any material from Fire Ant zones unless they have the proper permit (if in QLD)
- accept any material that may be infected with fungal pathogens like damping off, armillaria, phytophthora, etc.
Potential problems with Mulching
- Too much moisture can be stored in the soil and in the mulch itself for dry loving plants
- Matting and packing down of fine particled-mulches can actually repel water (this is called water repellency)
- Nitrogen draw down is believed to cause yellowing of leaves shortly after fresh mulch is spread. This theory is disputed by some authorities
- Some mulches (eg gums and pines) create allelopathic and antimicrobial properties which prevent growth of nearby plants and weeds
- Stone mulches can be thrown around by vandals
Source more helpful gardening information from subTropical Gardening magazine - www.stgmagazine.com.au
