The time has come to start the harvesting of many maincrop vegetables and fruits. Only vegetables like leeks, celery, Brussels sprouts and parsnips are left undisturbed for the winter months. These all benefit from frosting.

Clamping, although a very old method of storing a wide range of root vegetables, is still the most efficient. Carrots, potatoes, beet and other similar roots that are sound and healthy can be stored this way, providing they are not washed beforehand and are placed into the clamp directly from the soil.

There are slightly varying techniques involved with different crops but the principle is the same. A level area of ground is prepared in close proximity to a path and the roots without their foliage, are heaped up in an orderly fashion.

They are then given a covering of clean sand. Long straw, preferably the more resilient wheat straw, is then placed around the heap. The individual stems of straw are rested against the walls of the heap in an almost vertical fashion, but ensuring that a number are long enough to protrude above the apex of the heap.

Soil is then gently moulded over the straw to a depth of two or three inches, leaving the tuft of straw sticking out of the top of the mould in order to allow the free circulation of air within.

When completed, the soil is smoothed with the back of a spade and a shallow trench dug around the heap, to take away excess rainwater.

All root crops, with the exception of potatoes, can be stored in the same way. Potatoes only differ insofar as they do not require the addition of sand, but benefit from a layer of straw on the ground before they are heaped up, thus giving the effect of being totally enclosed by straw.

Later on, long keeping apples such as Newton Wonders and Bramley Seedlings can also be stored like this. However, it is important for the continued success of any clamp to replace the straw or sand and soil as you found them, after some of the crop has been removed for use.

Where only a few roots need to be stored, a clamp is unnecessary. Carrots, beet and turnips can be placed in boxes of clean sand and stacked in a cool dry shed. Potatoes are best kept in hessian sacks in the cool and dark, and stood on a board to keep them clear of the floor.

Lettuce for over-wintering can be sown during the next two or three weeks. These will stand unprotected and are intended for cutting next May or June. Imperial Winter and Arctic King are useful cabbage sorts, while Winter Density is a compact variety of the sugar cos type.

Once the seedlings have emerged they should be protected from the birds with wire netting pea guards and left unthinned until the spring. Winter spinach requires similar treatment, although the reducing of dense clumps of seedlings to more reasonable proportions is to be recommended.

WHAT'S NEW

Vivaldi is a strain of mixed wallflowers which flowers 16 weeks from sowing and in open weather is capable of blooming during January.

Peat-free Jiffy pots will be available for the first time this autumn.

Amour is a dwarf growing annual delphinium in pink, blue and white shades.

Q I have grown some lovely canna plants this summer. How can I keep them through the winter?

A Cannas are not completely hardy and are best lifted once the foliage dies back naturally and stored in a box of peat in a cool frost-free place.

Q My potatoes have produced some tomato-like green fruits. Should I take them off?

A In some seasons potatoes do produce fruits. These produce seed, but not the "seed" potatoes that gardeners plant. These are tubers. Remove them as they are making an unnecessary drain on the plants' resources.

QI have grown a mimulus cardinal flower. How do I propagate it?

ASeeds can be sown in the spring under glass. However, it is easily increased from stem cuttings taken now which will root quickly and can be over-wintered on the window ledge.