Mulching means covering the bare soil between plants with loose material. If the main aim is to improve the soil and feed the plants, use compost, leaf mould or farmyard manure. But if both the soil and the plants are fine, how about an ornamental mulch?
reduce moisture loss in summer,
and provide a decorative finish to set off the plants.
There are aggregates such as shingle, gravel or slate in a variety of colours and sizes. They are best spread over weed-suppressing fabric which will let the rain through but will keep the weeds out. And it will stop the aggregate disappearing into the soil over time. Of course, holes have to be made in the fabric for the plants.
Then, there are the biodegradable mulches which, apart from helping with the weeds, moisture and the look, will also:
improve the soil structure,
encourage beneficial soil organisms,
feed the plants.
In this category you have chipped bark, in several chip sizes, available from any garden centre or online for larger quantities. Or, as a cheaper option, seasoned woodchip bought from your local tree surgeon, however quality varies greatly.
These mulches break down gradually, releasing plant nutrients into the soil. As they do so, they need topping up. They last longer if spread over a weed-suppressing fabric but make sure all the edges of the fabric are hidden well or birds will pull them out!
The best time to apply mulch is when the ground is moist, mid or late spring (March – April). For aggregates, you will need a layer of about 1 inch (2.5 cm), or a thicker layer of 2-3 inches (5-7.5 cm) for chippings.
Before mulching, make sure the ground is weed-free. Otherwise, even with the fabric, buried weeds may find their way out, e.g. through the planting holes.