A look at the positives of applying Charles Dowdings' no-dig approach to gardening - plus, find out what else needs doing in the garden this week.

By Hannah Stephenson

Each autumn, there's a collective, nationwide groan as gardeners think about the endless digging they'll be doing over winter to improve their soil's condition for the following year.

But Charles Dowding, renowned market gardener and expert vegetable grower, can offer them some good news.

Over the years, he has conducted many experiments comparing the effect on plant growth of digging with not digging and has found that a 'no-dig' approach is the way to go. It not only saves time and exertion on digging, but also on weeding, because far fewer weeds grow on undisturbed soil.

He insists that growth and quality are improved by simply covering beds with 2.5-5cm (1-2in) of compost over the surface.

"The usual recommendation is to dig or even double dig the soil for growing vegetables," he says. "Because this is repeated so many times, most gardeners accept the task without wondering if it is really necessary. In fact, there is no need to dig at all."

Initial clearance of weedy and grassy ground can mostly be achieved with mulches (such as cardboard and compost) and some digging out of woody plants, then you can maintain the plot by weeding regularly. Surface compost weathers to a soft mulch over winter and can be directly sown or planted into, he adds.

"Soil does not need to be mixed, stirred, scraped or tickled. Only large lumps of organic matter on top require some knocking around with a fork or rake to create an even surface, mostly in winter and spring."

Dowding has run an experiment since 2007 to understand the effect on soil of digging and not digging, comparing growth of the same vegetables growing side by side in dug and undug beds.

"In the absence of digging, I have found that harvests are as high, sometimes higher, while some extra quality of growth on undug soil may be apparent.

"Soil in the undug beds, with compost on its surface, is well-drained, retains more moisture in dry springs and grows fewer weeds and stronger vegetables, especially at the start of the season," he explains in his new book Veg Journal, which offers month-by-month no-dig advice.

A key point in the no-dig approach is that undug soil is firm, which is not the same as compacted; roots have freedom to travel and are well-anchored at the same time.

"Fertility is enhanced by an increase of undisturbed soil life, which mobilises nutrients and helps plant roots to access them," he continues. "This is most noticeable in early spring, when growth on undug soil is generally faster by comparison with dug soil, whose fertility, in terms of soil life, is still recovering from the winter digging."

In experiments he found that during spring and early summer, many vegetables on the dug beds, especially radish, onions and spinach, started growing more slowly, and that in the undug beds the leaves of spinach and lettuce were thicker and glossier, the radish roots were shinier and the onions had a deeper colour.

He says that firm soil is often wrongly labelled as 'compacted', yet soil which has been mechanically loosened and fluffed up is not stable, which is why you have to walk on planks after digging heavy soil to avoid compaction.

Compacted soil is squishy when wet, rock-like when dry, contains few or no worm channels, is hard to crumble in your hand and may smell sulphurous because of lack of oxygen. It usually happens in the top 15-20cm (6-8in) of the surface and if it does, he advises adding plenty of organic matter.

He concludes: "My advice is simple: disturb your soil as little as possible."

:: Charles Dowding's Veg Journal is published by Frances Lincoln on February 6, priced £14.99

Best of the bunch - Helleborus niger (Christmas rose)

It may not flower at Christmas, but the Christmas rose is a welcome sight in January, producing large, saucer-shaped blooms with a central area of golden stamens. The largest flowers are borne by 'Potter's Wheel'. Place them in a sheltered spot close to the front of the shrub border, where nearby evergreens can protect them from winter winds and where you can see the flowers at their best. The bold, evergreen foliage acts as good ground cover and should keep its shape for the rest of the year. The Helleborus niger prefers light shade with humus-rich soil. It's a magnet to slugs and snails so make sure you are vigilant.

Good enough to eat - Shallots

Shallots are delicious pickled in balsamic vinegar or added to rich casseroles, so if the weather is mild and the soil is dry enough to work, you should be thinking about planting shallots. If conditions don't allow, wait another month or two.

Shallots should be planted like onion sets, with a trowel, as individual bulbs just below the surface in well-prepared, raked ground, around 15cm (5in) apart, leaving the tip showing. They will succeed on most well-drained soil, which has had plenty of organic matter added the previous autumn. Each shallot should surround itself with a cluster of five to six offsets that will plump up easily.

Shallots can't compete with weeds so you will need to hoe or weed the area by hand and make sure you don't break the leaves when weeding.

In most years, they shouldn't need additional watering in summer, although keep an eye on them in prolonged dry spells and if the soil is exceptionally dry, give them a water.

In July and August the foliage will start to yellow and fall over naturally. Lift the bulbs with a fork to break the roots and leave them on the surface to ripen fully in the sun. In wet summers, cover the bulbs with cloches or move them to the greenhouse to complete their ripening.

Good varieties include 'Golden Gourmet', which has a good flavour and will keep well, and 'Griselle', a French type renowned for its flavour.

What to do this week

:: Complete the pruning of greenhouse vines while they are still dormant and remove loose bark which may harbour pests.

:: Bring in pots of forced bulbs for indoor flowering when ready.

:: Protect winter-flowering bulbous irises in the garden from severe cold or damp.

:: Start forcing pots of lily bulbs for Easter and early summer flowering.

:: As cyclamen flowers go over, remove the stems by giving a sharp tug, which should remove the whole stem.

:: Take hardwood cuttings of blackcurrants, redcurrants, white currants and gooseberries.

:: Renew grease bands around fruit trees, if they have been in place a long time, to protect trees against winter moths.

:: Pick yellowing leaves off Brussels sprouts and other brassicas promptly, to prevent spread of grey mould and brassica downy mildew.

:: Bring container-grown shrubs like camellias into a cold greenhouse for extra winter protection.

:: Sow seed of slow-maturing half-hardy summer bedding plants including pelargoniums, begonias and verbenas, in heated propagators.

:: Start keeping a gardening diary and record book and update it each week.

:: Buy in well-rotted farmyard manure or mushroom compost to mulch borders and dig into soil.