Yes yes yes, all the good gardeners say this is one of the gardening laws!

Mulch is anything, which can be laid over the soil to reduce water loss, prevent erosion and inhibit the germination of weed seeds.

Some mulches also improve the quality and fertility of the soil, helping you save on fertilisers as well.

Organic mulches

Organic mulches are made from matter, which was once alive or part of a living thing. Over time, they break down into humus, the vital ingredient that all fertile soils contain.

Examples include compost, manure, lucerne hay, straw, leaf litter, shredded garden waste, grass clippings, composted sawdust and bark chips.

Inorganic mulches

Inorganic mulches were never part of a living thing and while they do reduce water loss and suppress weeds they cannot contribute to the health and fertility of the soil.

Examples include gravel and black plastic sheeting, neither of which is recommended today.

Why mulch?

>Less watering, better growth
All types of mulch work much like a blanket over the soil. The blanket protects the soil from the drying effects of sun and wind and also keeps the soil cooler. Moisture stays in the soil longer so you'll need to water less often. Mulch also remains warmer in winter. The mulch stabilises soil temperature, eliminating extremes of heat and cold so plants keep growing longer.

>Fewer weeds
Mulch can kill existing low weeds by preventing light from reaching them and, if the mulch is deep enough, weed seeds that germinate in the soil expire before reaching the light. Weed seeds that do germinate are easy to pull out. Weeds that arise from bulbs, tubers or perennial roots (onion weed and clover) will push through any layer of mulch. 

> Better, healthier soil
When an organic mulch is spread, worms and other soil organisms begin to feed on it. As it passes through them it is further enriched and distributed through the top layers of soil, raising the fertility and causing soil particles to clump together into bigger crumbs. Bigger crumbs of soil have greater air spaces between them so soil that is regularly mulched with organic matter becomes healthier, more open and better drained.

>Application
After weeding, apply new mulch at least once a year in a 3-10cm deep layer. Leave a few centimetres clear around the trunks of shrubs to avoid collar rot in some species. Always apply mulch over moist soil and wet the laid mulch to settle it in.

It is best to apply organic matter when it is old or rotted, not when it is fresh or green. Fresh or green mulches can actually cause harm by burning or by taking nitrogen from the soil. Always pile up fresh material for a few months before spreading.

>In pots
Mulch can save time and money spent on pot plant care, too. Layer to a depth of 2-3cm and keep the mulch away from stems and trunks.

Types of mulch

Lucerne hay, straw
Advantages: Relatively cheap. Good for smothering weeds.

Disadvantages: Hard to get in cities (try produce stores, stables, riding schools). Straw is not as nutritious as lucerne hay. Can be dusty to apply and for safety you should wear a dust mask.

How to use well: Bales are tightly packed and the straw breaks off in pads like tiles, making it easy to lay around plants. Make each 'tile' as thin as possible. Wet down after laying. Good ingredient in compost heaps.


Commercial composts, soil conditioners, etc
Advantages: Fully composted and often enriched with other ingredients. Easy to scatter about and conveniently bagged.

Disadvantages: Bagged types sold at nurseries can be costly for use in larger gardens. Landscape supply companies can deliver bulk quantities quite cheaply.

How to use well: Shovel the material onto the moist, weeded soil and spread into an even layer 3-5cm deep. Water after laying and re-mulch often.


Manure
Advantages: Can be free or cheap from riding schools, stables, racecourses or dairies. Nutritious, easily broken down.

Disadvantages: Contains weed seeds, which will germinate, can be smelly for a day or two and can be damaging if applied when very fresh. Composted manure can be bought from nurseries.

How to use well: If old, spread in 10cm deep later around plants. Water in. Let weeds come up, then spend an hour pulling them out. Add to compost heaps.


Wood chips, wood shavings, sawdust, composted wood waste
Advantages: Take a long time to break down. Blend well with native gardens. May be available cheaply or free from timber merchants and sawmills.

Disadvantages: Not very nutritious and can deplete soil of nutrients.

How to use well: Wood chips are best used in new gardens to protect bare soil. Finer wood shavings, composted pine bark and sawdust break down faster and are more nutritious. For designer effects use Redwood chips dyed with ochre.


Pine bark
Advantages: Blends with most garden styles as a dense weed-blocking cover.

Disadvantages: Somewhat acidic. Can be water repellent. Low in nutrients.

How to use well: Choose from fine to coarse grades. Coarser grades can rob nitrogen from the soil, so add manure at the same time.


Grass clippings and garden waste
Advantages: Virtually everyone has a regular supply free. Clippings are full of nitrogen and other important plant foods.

Disadvantages: Both can contain seeds, which may germinate and infest garden beds. If applied thickly they can create a mat, which inhibits water penetration. You need a shredder to use garden waste.

How to use well: Cut grass often, before seeds have a chance to form. Pile clippings in a big heap. Moisten as you pile and turn once a week with a garden fork. After a few months, spread thinly over the garden. Garden waste should be piled up and left to rot down for at least a month before use. Both clippings and shredded waste can be used as an ingredient in your compost heap.


Compost
Advantages: Nutritious and immediately available to the garden. Good compost should have no trace of its ingredients.

Disadvantages: You need at least a cubic metre of material to make good compost quickly. Compost heaps take up space.

How to use well: Layer different ingredients thinly on top of each other. Use garden and kitchen waste, except meat and dairy products. Keep moist but not sodden. Use when completely broken down by spreading thinly around plants.