Because it’s THAT TIME OF YEAR, and I get a fair few questions about mulch, I thought I’d put what I do here. This piece originally appeared in my weekly newsletter.

Mulching can be a bit of a minefield, so here is my attempt at demystifying it.

What is mulch?

The word ‘mulch’ is used in gardening to describe ANYTHING that you put on top of your soil. So that could mean horse manure, or it could mean thick black plastic sheeting. These two things are obviously totally different, so it’s useful to split mulch into two groups: Organic and inorganic.

Organic mulch is a mulch that originally came from something that was alive; manure, grass clippings, shredded bark, compost, shredded newspaper…all these things will decompose over time and be incorporated into your soil by worms.

Inorganic mulch is a mulch that comes from something man-made or which doesn’t break down; plastic sheeting, shredded rubber tyres, stones, landscape fabric. These mulches are used to suppress weeds and/or to give a ‘decorative’ finish to a border but apart from preventing moisture loss, they don’t contribute to the soil structure.

Adding organic material on top of your soil and around your shrubs and trees is generally agreed to be of benefit to them, particularly as it helps to prevent evaporation. Depending on what you use, it can also add nutrients to poor soil, which is generally considered ‘a good thing’ (although NB you may not wish to have ‘rich’ soil if you’re trying to grow plants that thrive on poor ones!) Piling on extra organic material will also build up your flowerbeds, which can tend to ‘sink’ over time. It will also make it harder for weeds to come up and find the light, weakening them, and lastly, but importantly, a dark mulch will just make everything look totally glorious…!

What to use:

The best mulch is your own home-made compost, but most of us don’t have enough of that (if any). If you are buying compost from somewhere please be super-vigilant about its source; the last thing you want is to be applying a mulch made from plant material that contains anything ghastly like weedkiller. Similarly, if you are buying manure, you need to ensure that the animals haven’t been fed on anything that has been treated with herbicide, as this can travel through the bodies of some livestock. I use a mixture of bagged horse manure, which I use around the base of my shrubs, and topsoil (peat-free) which is easy to spread and the easiest option for me with a small area to mulch. My own compost is always spread under my shrubs and trees as and when it becomes available, and I also use my lawn-mowings at the back of my borders.

Mulching rules:

Mulch freely, as and when you want.

Know that it’s easier to mulch in autumn and winter, when there are fewer things in the flower-bed, than it is in spring and summer, when you’ll have to try and avoid tulips and the like.

Know also that the only ‘bad’ time to mulch is when it is very very hot, or very very cold. The reason for this is that a mulch will tend to lock in dryness or cold and amplify it, rather than helping to mitigate. So if you’re wanting to mulch in the heat, then do water first.

I do hope that was helpful!

x Laetitia