The other day I received a notice from my water firm telling me that there's no longer a hosepipe ban in my area - but that I still need to be waterwise.

It's a topic close to the heart of award-winning gardener Chris Beardshaw, BBC TV's Flying Gardener and two-times Chelsea Gold Medal winner, who is currently planning his show garden for this year.

"The most important thing that anyone can do now to save water is to add plenty of organic matter to the soil," he says. Organic matter is a magical substance like a sponge. It holds the minor particles of the soil to such a degree that water can't swill out.

"The more organic matter you add to the soil the better the soil will retain its nutrients."

Organic matter can consist of anything you've raked up, leaf mould, composted grass and trimmings, vegetable peelings, anything which has decomposed to the point of becoming crumbly and brown.

But he points out: "Gardeners should never apply large quantities of fresh, undigested organic matter to their plants. It is far better to compost it first.

"To illustrate the point, my grandfather was a great rose enthusiast and used to religiously apply fresh horse manure to his specimens as mulch. Over several years the plants became weak and pale, losing the enthusiasm to flower. The reason was the high carbon to nitrogen ratio of the fresh manure, about 40:1. If only he had used well-rotted manure, with a ratio of about 12:1."

Other soil improvers include spent mushroom compost, a composted straw-based waste product from commercial mushroom farming, which is highly alkaline so can be used to moderate pH but should not be used on ericaceous plants such as rhododendrons, azaleas and camellias.

Farmyard manure is a rich organic matter product but needs to be composted to stop it scorching plants, while wormcasts are high in humus, with high water and nutrient-holding capacity.

The topics of saving water and the wonders of organic matter are covered in Beardshaw's latest book, How Does Your Garden Grow?, a scientific guide for gardeners of all levels who want to create and maintain beautiful, healthy gardens.

He adds: "You don't have to dig organic matter into the soil, but let the micro-organisms do all the hard work. If you improve your organic matter content by five per cent you can have a 50 per cent increase in the water-holding capacity of your soil."

Ideally organic matter should be added in autumn and will have been broken down into the soil by spring, but you can also add it now around the crowns of herbaceous plants and round the canopies of trees and shrubs.

Reapply it in 12 months' time and one heavy dose once a year should help the garden look after itself, keep the weeds down and warm the soil. Bad watering can be worse than none at all, he warns.

"Occasional sprinkling encourages roots to grow close to the surface, where they become prone to drought. Far better is deep watering, applying high levels of water over a long period to encourage thorough wetting of the soil at depth." Of course, many gardeners are now opting for drought tolerant plants including ceanothus, allium, hebes, sedums and buddleia, as well as pelargoniums, but you can also opt for many plants and herbs with scented leaves.

Other waterwise moves include ensuring the downpipes on your house are linked to a water butt, and don't dig the ground if it's not necessary. You will just end up exposing the moist underground layer to the elements.

* How Does Your Garden Grow?, by Chris Beardshaw, is published on April 26, priced £20.