DURING the winter and early spring most gardeners regard the unheated greenhouse as unusable. In fact, it often turns into an extension of the garden shed. A place where the folding summer chairs, the bicycles and the stepladder are stored.

While it would be unwise to suggest that it could be used as a place to raise seeds or cuttings without sufficient heat to keep it frost-free, it can nevertheless be a source of great winter enjoyment. Providing that the greenhouse has adequate ventilation, it is an excellent place in which to grow alpine plants and dwarf bulbs. The majority of gardeners are fascinated by hardy miniature plants, but most confine their cultivation to the rock garden. A quite natural place for them to grow, but one where the flowering period is governed entirely by the weather and you have to get down on your knees to fully appreciate their delicate beauty.

While the vagaries of our North-East climate cannot be totally overcome by growing such plants in an unheated greenhouse, even a minimal amount of protection is capable of advancing flowering by two or three weeks. The blossoms which are produced also being completely undamaged by hail, wind, rain or snow.

At the raised level of a greenhouse bench they can be much more fully appreciated, the colourful detail and often delightful scents of these plants which usually go unnoticed giving the most enormous pleasure.

The plants that are grown this way are not special, nor do they require complicated cultivation. They are conventional rock garden plants which are potted into shallow pots or pans in a free-draining soil-based compost and managed rather like a houseplant. Most are readily available at garden centres now. Heat is undesirable, for this distorts their character, usually to great disadvantage. What is required more than anything is freedom from dampness. Most alpine plants detest damp conditions. In the wild the plants are safely tucked under a blanket of snow from October until March or April. As the snow melts, the plants blossom and then grow on successfully.

Our climate is very unpredictable, both heavy snow and thaw occurring within days of each other and temperatures fluctuating wildly. The autumn to spring conditions experienced in the mountains can occur in a single day here in the North-East and the plants often become saturated.

In an unheated greenhouse, providing that the temperature is kept as low as possible by ventilating freely, near-perfect conditions can be provided. Ventilation which ensures the constant free circulation of air is the key to success. Only close down the greenhouse in damp foggy weather or when it is freezing very hard.

As long as it is appreciated that during winter and early spring only sufficient water to sustain the plant is necessary, rather than liberal amounts to promote growth, few problems will be experienced.

The plants need only remain in the greenhouse until flowering has finished, being consigned to a sunny cold frame or sheltered corner for the late spring and summer months. As autumn approaches they should be tidied up, repotted if necessary, and then returned to the greenhouse.

Philip Swindells

Q The hyacinths I have grown for Christmas have become very floppy but are otherwise fine. What is the cause?

A Too rapid forcing. If the bulbs are subjected to warmth and the light is poor they will become elongated. It is best to force hyacinths slowly with as good light as possible and cool conditions.

Q Can you recommend a giant exhibition onion variety that I can successfully sow indoors now?

A The two varieties widely grown by exhibitors are 'Kelsae' and 'Robinson's Mammoth'.

Q Unfortunately my maidenhair fern has dried out and looks very sick. I have watered it, but it is not recovering. Any advice?

A Repot your fern in a soil-less compost, teasing out some of the old compost from amongst the roots. Cut the tops off to within in of compost level. Keep well watered and it should recover.