Mulch is a very important component of a healthy garden, and particular important in our harsh Australian climate, especially in times of drought and summer months.
Mulch stabilise soil temperatures in the root zone, it suppress weed growth and it assists with water retention in the soil.
Mulch has numerous benefits to your garden:
- Helps retain moisture, prevents evaporation.
- Stops soil from blowing, or washing, away.
- Organic mulch adds necessary soil components as it decomposes.
- Cuts down weeds, by blocking light needed for weed seeds to germinate
NOTE - this also applies to seeds you wish to plant, so don't mulch heavily until plant seeds have well and truly sprouted.
- Weeds also pull up out of soft mulch much more easily than soil, especially if it becomes compacted.
- Keeps soil temperature more consistent- insulates against cold and heat.
- Helps lessen soil borne fungal diseases reaching plants.
- Keeps garden beds looking neater and natural.
Mulching tips Before mulching, remove any grass, weeds and dead plants from the bed. Put in any new plants before applying your mulch layer. If installing an irrigation system, such as a drip system, do so before mulching. Mulch to a depth of 75-100mm (3-4") deep. Mulch can be applied at any time, but is best applied in mid spring or early summer. Do not pile mulch up against the stems and trunks of plants. Piling mulch against stems can lead to trunk rot. While mulch helps to retain soil moisture, mulched gardens still need watering (water restrictions permitting). Top up the mulch regularly to maintain desired thickness.
To summarise
1. Weed area first.
2. Don't mulch too close to tree trunks or plant stems, or they may induce “Collar rot.”
3. Don't mulch heavily where you have planted seeds or tiny seedlings, they need light to get started
Types of mulch
Organic mulches break down and release nutrients into the soil. Examples include lucerne hay, pea straw, rice hulls, mushroom compost, leaf litter, compost and composted pine/gum tree bark.
Inorganic mulches such as pebbles, rocks and boulders look good and keep the ground underneath cool and moist. They are often used around cacti and other succulents that do not require additional organic matter.
Organic Mulches
Made of natural, organic materials, organic mulches add nutrients to the soil as they decompose.
COMPOST- Compost is like food for the soil! Making your own compost is a great use for vegetable and garden scraps. It can also be covered with another form of mulch for a more attractive appearance, if desired.
LAWN CLIPPINGS- These can be added to the compost making process, or used as mulch as is. High in nitrogen, so great for veggie patches. Allow to dry first and don't apply to thickly. Don't use lawn clippings which have been sprayed with any type of poison, and be careful not to include any runners from running grasses, or these will often take root and grow in your garden.
LEAVES- Once again, these can be pre-composted, or used as mulch as is. Partially decomposed or crumpled leaves are best, as they don't blow away as easily or mat. Pine needles can be used for the right kind of plants. some gardeners find that they help discourage slugs, as the little creatures don't find crawling over the spiky needles pleasant- makes sense!
SAWDUST- Older sawdust is best for garden mulch. If plants show signs of nitrogen lack, add a nitrogen rich fertisliser.
WOOD CHIPS- Very attractive mulch. Once again, aged chips are better, to safegaurd from toxins and fungal contamination.
BARK- Another eye pleasing and long lasting mulch. Eucalyptus and pine bark are commonly used.
STRAW/PEA STRAW/
TOPSOIL- Good topsoil sold at garden centres etc can be an excellent addition, as it contains lots of organic matter which helps insulate, retain moisture, and provide nutrients as it decomposes- everything you want in a mulch. However, make sure that you are buying good quality organic topsoil!
MANURE- Dry, well rotted manure is a good addition. If it is at the right stage, smell should not be a problem. You can add it to your compost or use as is. Cover with another more attractive mulch if the sight does not appeal. We use pelletised anure/ fertiliser pellets there are several brands out there but we use Katek Supa grow because its an organic product.
NEWSPAPER- Sheets or shredded newspaper (uncoloured ink), which is, of course, made from wood, can be very useful in the garden, especially under other more attractive mulch. Great for cutting down weed growth. Ideal for veggie gardens too.
Inorganic Mulches (man-made)
Made from man-made materials, these work well at their mulching job, are long lasting (sometimes almost forever), but do not add anything useful to the soil.
RECYCLED RUBBER- Made from 100% recycled rubber, this is safe long-lasting and natural-looking. Rubber mulch helps retain moisture, controls weeds, moderates soil temperature. Available in various natural shades, to imitate the appearance of bark. Doesn't blow away easily, and works efficiently so a lesser depth is needed.
PLASTIC SHEET- warms the soil, which accelerates plant growth. Stops water escaping and weeds from growing. As it is waterproof, irrigation needs to be done from underneath. Can overheat roots, or retain too much moisture, so caution is required. Plastic is well suited for use in vegetable gardens.
SCORIA/STONES/GRAVEL- Neat, but less natural appearance. Good mulch for a specific landscaping style. Very long lasting mulch. Be careful that pieces don't get into your lawn, or they can be a danger in lawnmowing. Offers a neat appearance but may not blend with every landscape design. They offer some weed control.
WEED MAT- Good for controlling weed growth. Allows moisture and air to reach plant roots. Can be covered with bark or scoria etc for appearance.
Further information
Composted horticultural tree/leaf/ bark mulch costs about $70 per cubic metre from landscape suppliers.
Question: How much to Mulch do I need?
Answer:
1. Find the measurments of the area to be mulched (use either a tape measure or pace it out). So say the garden bed is 10m x 1.5m, or 15 square metres.
2. For a mulch 4" /100mm deep this equals 1/10 of a metre, so divide the square area by 10. In this case, 15 square metres divided by 10 gives us 1.5 cubic metres.
3. Round up that figure and order 1.5 cubic metres of composted tree mulch to mulch the garden bed. This will cost about $100.
Question: Is it safe to use newspapers as garden mulch or put them in my compost pile?
A question I commonly receive regards the safety or lack thereof of using newspapers as mulch or putting them in compost piles. To provide an answer, we have to determine exactly what type of newspaper we're talking about.
Answer: Old newspapers were not safe for mulch or compost, because of the composition of their ink (which included toxic cadmium, lead and chromium). But most newspaper inks of the 21st century are soy-based and regarded as safe. To make sure, call up the newspapers in question and find out if they use a soy-based ink. If they do, the newspapers are safe for mulch and compost. If you wish to be a real stickler about it, ask a separate question regarding their colored pages (if any), the inks for which may or may not contain harmful ingredients. As a rule I tend to avoid coloured glossy papers.
Question: What is the difference between compost and mulch?
Answer: Compost should be worked into the soil (eventually, at least) to make it more fertile. Mulch, by contrast, is spread atop the soil, both to protect the soil from the elements and to suppress weeds. While it is true that organic mulches will eventually decompose, thereby themselves becoming compost, their function as long as they serve as mulch is distinct from the function of compost.
