30 Reasons for using mulch
- Improves soil conditions: binding sands and opening up clay
- Conserves soil moisture – mulch can save 73% of what might be lost through evaporation!
- Improves soil drainage
- Keeps soil temperatures cool during the day, warm at night
- Protects plants from frost injury
- Stops erosion
- Allows the soil to be worked earlier in the spring
- Saves time in cultivating and hoeing
- Prevents surface crusting allowing the soil to breathe
- Reduces soil compaction
- Holds down weeds
- Prevents hardpans being created in the earth
- Provides nutrients, gases and other growth substances
- Prevents vitamin loss in plants
- Encourages nutrients to be taken up by the roots
- Improves the yield of crops
- Stops nutrients from being leached from the soil
- Hinders pests laying their eggs near to the plant roots
- Deters harmful insects by its odour
- Reduces losses caused by soil-borne diseases
- Encourages earthworms and other microorganisms
- Causes feeder roots to develop near the soil surface
- Encourages roots to penetrate deeper in search of food
- Stops plants wilting
- Shades seedlings from sunlight
- Makes plants more sturdy
- Improves the flavor and keeping quality of the harvest
- Protects the produce from mud-splash
- Recycles waste
- Improves the ‘look’ of the garden
So, there you have it, mulch is much, much more than just about saving water! A fantastic weed suppressant, mulch is the key to a low maintenance garden. The correct selection of mulch can also increase the level of nutrients in the soil. Mulching weeds and feeds plants in the one operation!
Mulch is simple to apply. Weed the garden bed, water and spread the mulch around, taking care to leave at least 10cm clearance around the base of the plants. Water well after application. For best results, top up the mulch layer at least once a year as it decomposes into the soil.
A simple rule is, the faster the mulch breaks down, the better it is for the soil, although if a long-term mulch is required, slower decomposition may be the preferred option. Scientifically, things breakdown according to the carbon/nitrogen ratio. The lower the carbon to nitrogen ratio, the faster the materials are broken down and the nutrients released to the soil. These levels can be estimated by looking at the mulch. The denser the structure, generally the higher the carbon content, and the longer it takes to break down.
A QUICK GUIDE TO COMMON MULCHES …
There are many different types of mulch available. In order to determine the best mulch for your garden, you must consider what you want the mulch to achieve, for example, only weed reduction and water conservation, or also helping your plants to grow. Some of the more common mulches are listed with a quick guide to which to choose.
Organic mulches can be created from either living or dead material. They will generally decompose in the soil, and can provide valuable nutrition for the plants. They suppress weeds, act as an insulator to ‘even out’ soil temperature and conserve water.
All organic mulches conserve water by reducing evaporation due to sun and wind, suppress weed growth, and encourage worm activity. Organic mulches hold and retain water for later use by the plants. Even the uneven surface of most mulch acts to prevent water run-off, helping the water to be absorbed into the soil.
Carbon/Nitrogen levels are noted in brackets. Note: the lower the first number, the faster the mulch decomposes and provides greater nutrients to the soil. The higher the first number, the longer lasting the mulch.
LUCERNE (12/1) Lucerne (alfalfa) is the ‘prince’ of mulches, having a low carbon/nitrogen ratio. It is a mulch which breaks down quickly and adds substantial nitrogen and other beneficial elements to the soil. Lucerne breaks down to feed plants, stimulate biological activity and improve the sil structure. An ideal mulch or feed for roses and shrubs, it also acts as an activator for compost. For best results, buy lucerne which has been chopped into small pieces, otherwise the stalks can be very woody. As it decomposes quickly, it will need topping up more regularly than other mulches.
ANIMAL MANURE (12-20/1) All manures are great mulches. Fresh manure must be used cautiously as you can burn plant roots and it often contains weeds. Can have a strong odour so consideration needs to be given to the wind direction from your garden to your home! Any type of animal manure is best left to mature for a month or more prior to application to the garden – ideal for application to the compost heap layers!
PEA STRAW (25/1) Another nitrogen rich material, it breaks down quickly and conditions the soil. Pea straw is ideal for the home gardener to use in the vegetable patch, around fruit trees, shrubs and rose gardens. Pea straw may contain a few pea seeds that will self-germinate. These can be easily weeded out or left to grow to provide natural nitrogen to the soil. Use a ‘biscuit’ of pea straw on the border of garden beds to reduce the incidence of birds flicking the pea straw off and exposing the soil.
SEAWEED (25/1) Ideal mulch with long-lasting properties. Thought to be beneficial in reducing pests and diseases and must be thoroughly washed prior to application to remove excess salt. When using as a soil conditioner, mix with soil or manure in a compost to help it break down quicker.
LEAF LITTER (60/1) Leaves provide excellent natural mulch, particularly if fallen from the trees within your garden. Like wood chips, the plants can have a strong preference for related leaves as mulch. Native plants for example, would prefer their own litter as mulch!
SUGAR CANE MULCH (60-80/1) A good mulch but can be quite acidic so exercise caution and restrict application to those plants which are not sensitive to acidic soil conditions.
WOOD CHIPS/PINE BARK (100-500/1) One of the most readily available mulches – they break down slowly, changing colour as they weather. Many plants are particular about the type of wood chips used near them, for example, Australian natives don’t like mulch from oaks, elms or pines, yet respond well to mulch of their own variety such as eucalypts. An excellent long-lasting mulch – wood chips are economical for large areas!
STRAW (WHEAT OR BARLEY) (80-100/1) Crop straw is high in carbon and takes longer to break down so it is ideal to protect strawberries and vegetables from soil borne diseases. If this material was to be used more as a fertilizing agent, then a nitrogen source (manure, etc.) would be needed to help decomposition.
MUSHROOM COMPOST (31/1) A good-looking mulch material however, not particularly nutritious, nor cheap to purchase! Care needs to be exercised with the pH level – if it is too high (alkaline), it can restrict plant growth and cause leaves to curl. Not recommended for continual use – certainly not in the rose garden!
SAWDUST (500/1) Makes a good mulch and reduces weed activity. It does not absorb moisture if applied too thickly. If used as a soil conditioner, apply some nitrogen fertilizer as it uses the nitrogen in the soil as it rots. Use sparingly and do not use near plants which do not like acidic soil. Course sawdust should be reserved for weed-free pathways and playgrounds.
NEWSPAPER (170/1) Newspapers 4-5mm thick provide good weed suppression and moisture retention, however, they must be covered with mulch material and if using around roses, ensure that the newspaper is 10cm clear of the rose understock stem!
NON-ORGANIC MULCHES These mulches may be man-made materials such as plastic, or mineral substances such as gravel. They are generally water saving and help even out the soil temperature, however, they do not provide any nutrients for the soil and some such as plastic, can even starve plant roots of oxygen.
Gravel, scoria or pebbles are not recommended to use if you want to dig into the garden bed. Whilst conserving soil moisture and keeping ground temperatures even, these materials should have suitable weed-inhibiting mats under them and even then, weeds can be an ongoing problem!
Plastic might be excellent for keeping weeds at bay, however, it will encourage shallow root systems, stifles oxygen intake and definitely fails to add nutrient to the soil so is NOT recommended for garden beds!