THE LAZY GARDENER: Rob Foster writes about the value of greenhouses

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Most keen gardeners find it necessary sooner or later to invest in a greenhouse. Having one extends the growing season by giving you the opportunity of growing plants in a controlled environment and pest control is easier.

This allows you to overwinter many plants and get them off to a flying start in the spring, as well as giving you a place to retire when the weather is against working outside. Jobs such as seed sowing and transplanting will suddenly be a joy to do.

Now is the time to get a bargain as garden outlets and chain stores do not want to hang on to them over the winter period. However, the choice can sometimes be bewildering for the first time buyer.

Always choose the largest greenhouse you can afford, not forgetting that it has got to fit in the garden. Most greenhouses have either wood or aluminium frames. What’s the difference? Well aluminium requires less maintenance, and has a longer life.

Alternately wooden framed greenhouses have a shorter life, but they are far warmer and it is definitely much simpler to fix insulating material on the insides and also to install shelving if needed.

A very important fact, that is very often overlooked, is the need for adequate ventilation; manufacturers never supply enough vents for the amateur greenhouse, they are normally sold as extras.

Also consider investing in safety glass, particularly if small children will be playing near it.

When siting a greenhouse, select a sunny open site away from the trees, apart from the shade a broken branch in a storm can spell disaster if it falls through the glass. It is prudent to avoid open exposed sites which are subject to strong north or easterly winds which could cause rapid heat loss. Traditionally a greenhouse should be sited with a north to south alignment.

Plants really need acclimatising before being moved outside from the warmer environment of a greenhouse. So consider buying, or making, a cold frame. A cold frame provides a cooler environment and can be used as a halfway house to gradually acclimatise plants before moving them into the garden

If you do not want to go to the expense of heating a greenhouse then purchase one of the cheap little ‘patio type’ polythene greenhouses, and place this inside your greenhouse. This provides good frost protection as you now have a greenhouse in a greenhouse, increasing growing potential again. If you need to provide extra heat inside of this mini greenhouse then all it takes is a small heater, sold as sump heaters.

his will burn for weeks on a small amount of paraffin and avoids having to heat the rest of the greenhouse, but ensure you have adequate ventilation.

Jobs in the garden

Don’t delay this is the last chance to clip conifer hedges

Pick runner beans before they become tough and stringy

Check ties on trees, loosen if necessary.

Use slug pellets based on ferric phosphate they are safer

Now is the time to prune Wisteria

Harvest onions when the foliage collapses

Prune rambling roses after they have flowered

Keep dead heading annuals to prolong the flowering period