Mulch protects plants and trees from weeds, moisture loss and temperature damage. It must be applied at the correct depth around the plants or the benefits are minimal. Mulch can harm plants when applied too deeply by causing too much moisture to build up and inhibiting aeration to the soil beneath. The correct depth depends on the mulch and the types of plants growing in the mulch bed.
You should place mulch around all new plants to give them the best chance of settling in. Mulching is one of the most important ways to keep your plants healthy. Mulch improves and protects the soil, and reduces moisture loss. Mulching established plants should happen around early spring. This is when plants are beginning to grow, so improving the soil will help at this time.
Before applying mulch, it is a good idea to thoroughly weed the area. Spread the mulch to the desired thickness. Make sure you keep the mulch 5-10 cm away from stems of woody plants. Also, make sure that you keep a space of about 20-30 cm between the mulch and walls of buildings.
The amount of mulch depends on the size of your garden and on the thickness of mulch required. A standard application of mulch is around 10cm (4 inches) in depth. A premium application is around 15cm (6 inches) in depth.
Vegetable and flower gardens benefit from a mulch application for both moisture retention and weed suppression. The mulch also helps insulate the soil so it does not freeze quickly or become too hot and damage the plant roots in the bed. Garden plants require a mulch depth near 5cm (2 inches).
Trees benefit from a mulch depth between 5-6cm (2 – 2.5 inches). The thick mulch layer suppresses weed and plant growth under the tree while retaining moisture in the soil. Thicker mulch layers may retain too much moisture and cause surface roots to suffer rot, while a thinner layer supplies few benefits. Applying the mulch at the right depth is only part of proper application. The mulch must also cover the ground over the root system and beneath the tree canopy. Leave a 5cm (2-inch) space between the mulch layer and the tree trunk. Moisture in the mulch can cause the trunk to rot.