Mulch has a vital role in maintaining the health of your garden. It inhibits weed growth, slows water evaporation, moderates the temperature of your soil and in most cases, provides additional nutrients to the soil.

Mulch will also aid in preventing disease by reducing soil splash on your plants during rain.

But as with all things, there are right ways and wrong ways to mulch your garden. Here are just some guidelines to bear in mind when mulching.

Mulch can be organic or inorganic. Organic consists of previously living plant life like leaves, grass clippings, wood chips, sawdust, lucerne hay, straw and sugar cane.

Inorganic mulch consists of gravel, black plastic, weed control mats and decorative rocks and pebbles. Inorganic mulch has no place in your vegetable patch. It adds nothing to the soil and will get mixed into the garden bed.

However, it's worth having the discussion about what they are good for. You decide on the best option for each garden area you're working with.

Organic Mulches


Organic mulches are made up of something that was once living. Take care not to use anything that contains seeds. If in doubt, partially compost it first.

Organic mulches will break down over time so will need topping up between plantings and definately every season.

They can help with problem soils by adding organic material to too heavy, too sandy or nutrient poor soil.

Pros: Mulches will improve your soil and keep weeds down. They will moderate the temperature of your garden soil and maintain moisture longer.

Cons: If you are purchasing mulch, this can become an expensive option. But there is no real need too. Composting your own materials should provide plenty of material that is safe for the garden.

Concerns: If you are hoping to warm your soil in spring, mulch will hinder that.

Try to remove as much of the mulch as possible to allow warming sunny rays to hit the ground proper before planting. If using leaf mulch, make sure to compost it first.

Uncomposted leaves or grass clippings will mat and prevent water getting through to the plants underneath. Not all leaves are appropriate. Oily leaves, like eucalyptus or pine will break down very slowly and release an oil into the soil leading to water absorption problems. Fresh pine bark and sawdust can also cause problems due to oils and chemical treatments.

The source of your mulch is very important, so don't throw just anything on the garden.

Inorganic Mulch


Inorganic mulch can have a role in your garden, just not your vegetable garden. I'm not one to throw out the baby with the bathwater, so some pointers on where they are appropriate.

I hate black plastic. I really hate black plastic. It starves the soil underneath of the natural interaction with the environment around it. Rain can't get in and weeds can't get out...for a while. And let's be brutally's ugly and unnatural.

There is however, one use I can advise for black plastic sheeting. If you are in a cold climate and trying to warm your soil in spring, clear as much mulch away from the garden as you can and spread black plastic on the bed. It will speed up the warming process and kick start the soil activity underneath. Once you're ready to plant, put the plastic away for another year.

For container gardens, decorative rocks or tumbled glass can have a striking effect. These types of mulch should only be used in situations where you are not planning to dig around or disturb the soil. A bed of cacti or succulents is perfect for this situation.

Pros: Dramatic effects can be achieved with texture and colour. They will still have the effect of suppressing weeds and retaining moisture and on outdoor patios can produce a cooling effect. They can be expensive initially, but never need topping up.

Cons: They don't add anything of value to your soil so only use them when the soil doesn't need improving. They are also problematic when trying to fertilise your plants. Best option when using inorganic mulch is to pour diluted liquid fertilisers over them. If inorganic mulch gets mixed into your soil, it can be a real chore to sift it out.

'Leafmould' courtesy of Joel Gratcyk.
'White pebbles' courtesy of Damien King.