A mulch is any material, organic or inorganic, applied to the soil surface in a layer around a tree about 7.5 to 10 cm deep.
Mulch has many benefits:
- It reduces surface moisture evaporation.
- It creates a physical barrier that prevents weed growth.
- It prevents wind and water erosion of soil.
- It reduces soil compaction and prevents mud or rain splash on tree trunks.
- It can prevent damage from lawnmowers and string trimmers.
- In the spring, a layer of mulch lessens plant damage caused by alternating freezing and thawing conditions.
- In summer, mulch can cool the soil which promotes root growth.
Trees should have a large mulched area extending past the tree's root system which usually extends out as far as the tree is tall. However, leave a 'mulch-free' area 3 cm around your tree's trunk to discourage small rodents from chewing on the lower bark.
The most effective mulches are organic materials and can include:
- Grass clippings
- Wood chips/shavings
- Flax shives
- Bark chips
- Pine cones and needles
- Shredded bark
- Post peelings
Organic mulches are better than inorganic mulches since organic material can break down and decay, adding to soil fertility and improving soil structure. Since organic mulches must be topped up periodically, weed seeds do not get a chance to germinate.
Inorganic mulches - such as shale, gravel , rocks, bricks or lava rocks - can collect heat, causing hot zones. Inorganic mulches can look unkept when weed seeds and leaves blow in and collect. Gravel can cause iron deficiency or chlorosis in some woody plants.