I discovered the virtues of mulch several decades ago, thanks to a book by Ruth Stout: How to Have a Green Thumb Without a Aching Back. The timing was perfect, as I’d just had a horrible case of sciatica and was wondering how I was going to continue gardening.
The Benefits of Mulch
I immediately set about accumulating a supply of dead leaves in autumn, so as to have plenty of mulch for the following year, and I quickly realized how much the soil and plants benefit from this addition of organic matter, which is also free. Earthworms and other decomposers remain active under the leaf litter, which decomposes to enrich the soil as in a forest. The soil remains moist, even during heatwaves. Adventitious plants (i.e. weeds) no longer have light in which to germinate, and those that do show through the mulch are easy to pull out. Vegetables and flowers stay clean, even after heavy rain.
Bare soil dries on the surface and forms a crust. Cracks form and water from the lower layers reaches the surface and evaporates. This is why weeding is recommended, but it’s much better to apply mulch. In nature, as soon as the soil is bare, plants immediately cover it to protect it. This is the role of weeds, opportunistic plants that quickly establish themselves in the smallest vacant spaces. They generally produce a lot of seeds, which can lie dormant in the soil for decades, waiting for the opportunity to cover the ground. Of course, when you’re gardening, you don’t want weeds, and many gardeners regularly weed between their vegetables to keep the soil “clean”. It’s said that one weeding is worth two waterings, but mulch is worth at least five to ten waterings, depending on its thickness and renewal. Personally, I don’t need to water established flowers and vegetables during the summer.
Types of Mulch to Avoid
Many types of mulch are commercially available, but some should be avoided. These include inorganic mulches such as pebbles or volcanic stones, which do not improve the soil. After a few years, these mulches become dirty, accumulating leaves and other plant residues and becoming overgrown with weeds. Vacuuming and herbicides are then needed to keep them acceptable!
Types of Mulch to Use
But there are plenty of free materials you can use as mulch:
- Cut grass: it’s not very aesthetic and decomposes very quickly, but it’s easy to spread between small vegetable seedlings. Leave it to dry out on the lawn before use.
- Dead leaves: available in abundance in autumn, but harvest them dry and store them away from the elements. It’s best to shred them so they don’t blow away in the wind. Ideally, they should be harvested with a lawnmower (including the bag) or a leaf vacuum cleaner, which shreds them at the same time. They decompose in about 6 months, so wait until spring before spreading them out.
- Hay: available at low cost in the countryside, it is useful in the vegetable garden near established plants. Hay is full of wild plants, full of seeds and can contain some very unpleasant weeds. If you always have mulch on the ground, they won’t have a chance to establish themselves, but it’s something to watch out for. Hay decomposes between six months and a year.
- Straw: made from cereal stubble, it’s easy to find free in bales after Halloween. It should not contain many weeds and is a good option in the vegetable garden. It decomposes within a year.
My Personal Favorite
- RCW (ramial chipped wood), which I’ve already mentioned in another article and is available in profusion by calling local tree trimmers or even your municipality. For me, it’s the best mulch, free or inexpensive, an excellent soil conditioner and lasts at least a year. I use it mainly in perennial beds and around shrubs and young trees. I also use it in autumn in the vegetable garden to cover the soil over winter. It’s a very attractive mulch, provided it’s well shredded: which depends on the machine used and how sharp it is. You’ll need to shop around a bit for pruning companies in your area.
- Hedge clippings: leave them at the base of your hedges rather than buying commercial mulch. You can also run the mower over them, with the bag, and use this beautiful material where you need it.
What Thickness Do I Need?
The way you use mulch will vary according to the situation. Around trees and shrubs, for example, you can apply 7 to 10 cm of slow-decomposing mulch, taking care to keep it away from the trunk to avoid rodent damage. You can even apply 10 to 15 cm if you have an easy and inexpensive supply. For perennials and annuals, and in the vegetable garden, you can use 3 to 5 centimetres of not too coarse mulch.
Around seedlings, you need to be careful and wait until the young seedlings are strong enough before gradually approaching the mulch. Because if mulch prevents weeds from germinating, it does the same for our flower and vegetable seedlings. A thin layer of cut grass is ideal as soon as the seedlings have sprouted, and is easy to spread.