Louise Curley

13 Apr 2023 08:12

Magic Mulch


I’ve spent the last week or so wheelbarrowing four tonnes of compost from the front of the house to the back. It was hard work and I don’t want to have to do it again in a hurry but the beds in the back garden are all pleasingly covered in a thick mulch now, all ready for the new growing season ahead.

It’s cheaper to buy in bulk which is why I had so much delivered in one go and I wanted a particular type of mulch (fine bark) to help to the break up my heavy clay soil, so rather than going to the garden centre I had to buy from a specialist supplier. I do make my own compost but it doesn’t go very far so that’s another reason for having to buy it in.


What is a mulch?

A mulch is a covering that’s placed on the surface of soil in a border or in a container. The mulch can be one of any number of materials. Some can be non-biodegradable such as gravel or slate chippings, which tend to be used for decorative purposes, although they do have other benefits such as suppressing weeds and conserving moisture within the soil. Then there are the biodegradable mulches which include garden compost, leaf mould and composted bark. These suppress weeds and help to maintain moisture in the soil like the non-biodegradable ones, but they have the added benefit of feeding the soil and improving its structure as the material is broken down by worms and other soil organisms.

When should you mulch?

You can mulch your soil at any point in the year although it’s not a good idea to do it if the soil is frosted or waterlogged. I prefer to mulch in late winter or early spring, when I’ve cut back last year’s tired top growth on the perennials and the soil is at its barest. By mulching now you help to keep the winter moisture in the soil throughout spring and into summer, you also prevent a rash of annual weed seedlings popping up everywhere.



What are the best mulches?
  • Some materials such as manure and chipped bark should be left to somewhere to break down, ideally for six months, before being applied to the soil – fresh manure will be too rich and could damage plants and fresh bark can strip soil of nitrogen as it starts to break down.
  • Spent mushroom compost can be a good mulch but it contains chalk which makes the compost alkaline with a high pH. It can alter the pH of your soil, so it’s best not to use it on soil that’s already alkaline, and it is isn’t suitable for plants such as rhododendrons which need an acid soil.
  • Leaf mould is lovely crumbly stuff that’s created when leaves decompose. You can’t buy it, so you need to make your own, which is easy enough – simply fill some old compost bags with leaves in autumn, keep the leaves moist and stash the bags somewhere out of the way. In 12 months you’ll have a mulch you can spread on woodland borders.
  • Garden compost is great stuff but it can be full of weed seeds, and it’s hard to make enough of it.
  • Fine bark is very finely shredded bark which has a coarse texture that is great for helping to improve the structure of heavy clay soil.
Tips for mulching
  • Ideally it should be a couple of cm thick for it to suppress weeds.
  • Spread it around plants but make sure it doesn’t come into direct contact with woody stems as it can cause them to rot.
  • Don’t mulch dry soil, wait until it has rained so that the moisture is retained in the soil.