Gardening – Make mine mulch

Every indicator points to a windy, hot and dry summer this year, and our gardens are going to suffer more than normal. The excessive rainfall over the past couple of years has stressed out the root systems on many garden plants, leading to root disease and roots that are closer to the surface than normal. The most important step you can take now is to mulch your trees and gardens while the soil is still moist. I use just about anything I can get my hands on to use as mulch, with different products being used on different areas, depending on their characteristics.

We collect seagrass washed up on the beach after an easterly storm and lay this on the vegetable beds. Seagrass takes months to break down, so it is a good long-term mulch; don’t bother washing it as some people recommend, as the minimal amount of salt that it contains won’t harm your soil.

A layer about three centimetres deep will keep soil moisture in and prevent most weeds germinating, while new plants can be planted through the layer into the soil below.

Another good source of mulch are tree prunings that have been shredded through my chipper.

Woody mulches like this (or purchased bark mulch if you don’t have a chipper) are very good around fruit trees, as the woody matter feeds fungi and bacteria that are antagonistic to root diseases. Again, a layer of at least three centimetres is beneficial, up to about five centimetres deep. Aside from moisture retention, disease control and weed suppression, a woody mulch also provides a lovely layer of slowly composting material that tree feeder roots can grow into.

Grass clippings are a good source of mulch but, these need to be applied a little more carefully, as a thick layer of wet grass clippings can form a slimy anaerobic layer that prevents vital oxygen reaching the root system, potentially doing more harm than good. Additionally, grass clippings placed against the trunk can lead to collar rot. Grass clippings are best applied in a more doughnut shape around the tree and no thicker than three centimetres at any one time. As the grass breaks down, it does add nitrogen and other nutrients to the soil, which is a bonus.

Often, if I lightly prune something, such as a hedge or a shrub, and it’s too small to bother putting through the chipper, I’ll just spread the twiggy material directly under to act as an instant mulch.

This works very well and saves labour but does look a little messy for a while. I’ll do the same with banana leaves, heliconia leaves and cannas.

For those with tidier gardens than mine, a bark mulch is ideal. Some of these are pre-composted so will not take much nitrogen from the soil while they continue to break down. A raw bark mulch that has not been composted will take nitrogen from the surface layer of soil, which can lead to a short-term deficiency, although over time this tends to balance out. Overall, mulching is one of the most important jobs for a healthy, productive garden that is resilient to adverse conditions.