The process of using mulch is one of those gardening procedures that sounds as though it’s going to be complicated – but in fact mulching is actually a very simple concept. It’s easy to do and, best of all, it could save you hours of time on garden maintenance, whether you’re growing ornamental plants, fruit and vegetables, or a mixture of both.
There are two kinds of mulch: organic and inorganic. Both are laid on the soil around plants to lock in moisture and nutrients and to help suppress weeds. In winter, an organic mulch can also be used to protect the roots of more delicate plants.
Want to know more? Read on for our expert guide, then head to our plants and trees hub for more gardening advice.
What is mulch?
This includes well-rotted manure, garden compost, leaf mould and composted bark – pretty much anything that was once living material. You can buy products specially designed for mulching too, such as Lakeland Gold (made from bracken, and good for heavy, clay soils) and Wool Compost Double Strength (ideal for free-draining soils), both from Dale Foot Composts.
Organic mulches look great in the garden and as well as locking in moisture and suppressing weeds, they also improve the soil as they slowly decompose, helping to keep plants healthy so they grow more vigorously and are more able to fight off pests and diseases.
These include landscape fabrics and, more controversially, black plastic sheeting. Neither are as attractive in a garden setting as organic mulches and are more suitable for the veg patch, or where you need to clear a patch of ground of grasses and perennial weeds before planting into it later on.
Although inorganic mulches suppress weeds (arguably even more effectively than their organic counterparts) and help to retain moisture, they can’t play a part in enriching the soil as they don’t break down. There are now a few biodegradable options on the market, though, that can be used in the same way but can then simply be dug into the soil at the end of the growing season – try Mulch Organic.
What inorganic mulches like landscape fabrics and black plastic sheeting do very well is warm the soil in spring ready for the first fledgling vegetables to be planted, and then retain heat throughout the season – useful when you’re growing crops like aubergines and chillies outdoors.
Other inorganic mulches are ideal for adding to the tops of compost in pots, again to help retain moisture and keep weeds at bay – these include slate or stone chippings, pebbles and gravel.
How to get the most from mulch
Organic mulches need to be applied fairly thickly to be effective – between 5cm and 8cm deep is ideal. Remove all weeds first and water well if the weather has been dry. You can apply organic mulches over a whole bed or just around the base of individual plants or trees – in which case, try to extend the mulch out so that it’s the same diameter as the plant or the tree canopy.
If you’re using inorganic or biodegradable landscape fabric or sheeting, there’s no need to weed first, but do water well before laying it over the whole bed. Then cut crosses at regular intervals in the fabric and pop your plants in through these.
What type of plants are suitable for mulching?
In the garden, all shrubs, perennial and herbaceous plants, trees and fruit bushes will benefit from an organic mulch. And in the veg patch, young vegetable and salad plants will grow much better if they don’t have to compete with weeds for water and nutrients when a layer of landscape fabric is used as an inorganic mulch to keep them at bay.
What time of year should you add mulch?
You can spread mulch around plants at any time of year, but mid to late spring is ideal as annual weeds are yet to make an appearance then, so you’ll be smothering them before they have a chance to take hold. Top up the mulch whenever you notice it’s starting to look a little sparse. In autumn, spreading a thick layer of mulch around more tender plants like dahlias, gladioli, Verbena bonariensis and salvias means they’re more likely to come through the winter unscathed.
Avoiding problems with mulch
- Be sure the ground is moist (by watering it if necessary) before adding any kind of mulch – laying it onto very dry soil will just exacerbate the problem.
- Although almost any organic material that would otherwise go to waste in the garden can be used as a mulch, avoid fresh lawn clippings or newly pruned woody material – these take nitrogen from the soil as they decompose, leaving less for plant growth.
- In the first season, weeds often appear in the mulch itself as it may have already been harbouring seeds. These weeds will be very easy to pull out, and then shouldn’t trouble you again.
- Leave a narrow gap between the mulch and the stems of trees or shrubs – if it touches them, it may soften and weaken them, making them vulnerable to disease.
- Slugs can be a nuisance if they decide to use the mulch as a nice, warm place to shelter. Be vigilant and use slug control techniques to keep numbers down (beer in a shallow dish is one of the most effective methods).
Taking mulching to the next level
The ‘no dig’ method of gardening, especially in the veg patch, is gaining an ever-increasing following among gardeners. The idea is that you simply cover all your soil with garden compost or well-rotted manure as a mulch each year, rather than laboriously digging it over as is traditional. This feeds the micro-organisms in the soil without disturbing them, giving you a productive garden that's much less labour intensive. And there are fewer weeds too, because the seeds harboured in the soil haven’t been brought to the surface by digging.
The greatest exponent of the no-dig method is garden guru Charles Dowding. ‘Soil that you cover with compost is then aerated and drained by well-fed worms and other soil life, and it looks gorgeous,’ says Charles. ‘You are then free to concentrate on sowing, planting and harvesting: gardening becomes quick, easy and super productive.’