What is mulch?
The process of mulching is, at its most simple, the act of covering the soil with material. Depending on what material you use, mulching has a multitude of benefits and is one of those rare once or twice-a-year activities that the soil and plants in your garden will thank you for. Mulching is suitable for your annual vegetable beds and for your perennial plants, shrubs and trees. All plants benefit when you mulch!
What is mulch made of?
Mulches can be broadly divided into two categories - organic (made of natural material) and inorganic (made of man-made material) and there are benefits to both options.
Wood chip, well-rotted manure, compost and leafmould are all organic mulches, so called because they are biodegradable and will rot down into the soil below. Wood chip, when used as mulch, decomposes relatively slowly and so will protect the soil with the added benefit of not needing frequent reapplication. Leafmould - which is made from autumn leaves which have decomposed for a year or more - when used as mulch will improve the structure of your soil as well as its capacity to retain water although its nutrient content is low so if you’re looking to replenish your soil through mulching, compost or well-rotted manure are a better bet.
Whereas inorganic mulches are made of either fabric or plastic and as they do not break down, they can be used repeatedly, season after season if installed with care and stored well when not in use.
What’s the point of mulching?
While all kinds of mulch can be deployed to suppress weeds by depriving them of sunlight and to retain moisture in the soil by reducing evaporation, organic mulches have the important added benefit of enriching the soil as it is broken down by the soil life. This results in improved soil structure, replenished soil nutrients and eventually healthier, stronger plants. They also have the benefit of making your garden look neat and tidy - if you like that kind of thing!
While inorganic mulches tend not to be quite so nice to look at, they do have benefits of their own. They can be used to warm the soil in the spring ready for early season plantings or kept in place to cover the soil and planted through with warmth-loving plants like aubergines or chillies.
No dig mulching
As a no-dig grower myself, the process of annually spreading compost across my vegetable beds is the most important part of my growing year. This act is central to this approach to growing as the focus is on causing as little soil disturbance as possible. The idea is that by laying the compost (or well-rotted manure) on top of the soil and leaving the soil life to do the work of incorporating it (instead of digging it in), the soil will retain its natural structure and layers, dormant weed seeds will not be brought to the surface and all the nutrients and minerals used up that season will be replaced as this fresh organic matter is broken down.
Fabric or plastic mulches do have their place in no-dig systems though as they are especially useful before creating new beds when used to kill off perennial weeds like couch grass and bindweed.
How and when to mulch
Inorganic mulches need to be secured onto the soil using stones or gardening pegs, to prevent them from becoming displaced or blown away by the wind. Organic mulches like compost, wood chip or well-rotted manure are placed directly on the soil and should stay in place as long as the weather isn’t too disruptive as it settles onto the ground. To be most effective, organic materials should be applied at a minimum of 5cm thick.
I apply organic mulch once a year and while it is possible to mulch at any time, I tend to do so in either autumn or spring. I mulch my vegetable beds with compost when I’ve just removed one crop and am poised to plant another and then mulch my perennial beds at the same time. Fruit bushes and trees benefit especially from rich mulches like well-rotted manure so that the nutrients they need to produce a harvest are readily available to them.
Mulching in containers
If you’re growing annual crops or flowers in pots, it’s likely that you’ll replenish the compost entirely every season. But if you’re growing perennial plants in containers or annuals in larger planters, mulching is as worthwhile for them as for plants growing in the ground.
The nutrients in the soil in your pots and planters will need to be replenished after plants have been growing in it for a season and organic mulches like compost or well-rotted manure can reinvigorate your containers ready for the following year’s growing season.
Possible problems with mulch
- It is really important to remember that the condition of the soil will be retained under the mulch you lay down so ensure that the ground is not frozen, is free of weeds and is well-watered before mulching.
- When mulching around trees and woody shrubs, be sure not to lay the mulch against their trunks and stems as this can cause water to gather, lead to rot and increase your plants’ susceptibility to disease.
- Weeds can find their way into your organic material so keep an eye out for germinating seeds in your mulch and remove them before they are large enough to really root down.
- Mulch can provide a cosy spot for slugs to make their home so keep an eye out for signs of their presence and if needed, use yeast or beer traps to keep them in check.
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