What are the benefits of mulching?
There are several benefits that come with mulching. The primary benefit is the way it suppresses weed growth, thanks to its blanketing effect – most weeds can’t push through the mulch layer and those that do make it are weak and can be easily removed by hand. In addition, weed seeds can’t get through to the soil to germinate.
Mulches also have a beneficial effect on soil temperatures by reducing the wide fluctuations that occur at surface level, from baking hot during the day to cold at night. This means less stress for the plant roots, too. And a healthy garden is all about healthy roots – they’re the powerhouses of your plants!
How to mulch your garden
With mulch, there’s a ‘just right’ quantity. Too shallow, and it won’t do its job; too deep, and water can’t get through to reach the soil. As a rule of thumb, spread a covering 2–5cm thick, using the higher level for coarse mulches such as chunky barks and wood waste products. Keep finer mulches like shredded straw to about 2–3cm, as thicker layers can pack down and become a water-repelling blanket – the opposite of what you want.
5 types of mulch to consider
Use your compost as mulch. Simply spread it around the garden, applying it up to 40mm deep. Compost has great evaporation control and is good for adding humus to the soil. It is more expensive than other forms of mulch, however this is a great option if you have a compost bin and only have a small area to mulch.
2. Pea straw
Pea straw mulch is ideal for roses, flowers, vegetable gardens, trees, shrubs and fruit trees. This type of mulch stimulates growth and insulates roots from weather extremes. It does break down quickly and will need to be topped up on a regular basis. It is high in nitrogen, so pea straw mulch is ideal for poor soils. Pea straw is generally sold in bales, is easy to handle and transport.
3. Sugar cane mulch
Sugar cane mulch is made from dried sugar cane leaves and tops and is sold in bales. It is less expensive than other mulches, easy to handle and more readily available. This type of mulch breaks down quickly, encourages soil organisms and is good for vegetable gardens. Top it up regularly.
4. Barks and woodchips
These type of mulches take longer to break down so it’s more economical, as you don't have to apply it as often. Barks and chips are best used around established plants like shrubs and trees where immediate soil improvement is not required. Wood-based mulch can cause nitrogen deficiency, which causes plant leaves to turn yellow. This can be overcome by adding blood and bone, which adds extra nitrogen to the soil.
5. Pebbles and gravels
If you want to go a long-lasting mulch, pebbles and gravels work well. This includes products such as scoria, gravel and stone river pebbles This type of mulch is best suited to succulents and Mediterranean-type plants like lavender. It won’t improve the soil structure, but it will help reduce soil evaporation.
How much mulch you should apply, depends on the type of mulch you use. As a guide, you should apply between 2 and 6 centimetres of coarse mulch. Straw mulch can be applied thicker.