The Herald - The Herald Magazine
GARDENING
AGREENHOUSE is an all-yearround winner in any garden. It gives you early sugar peas, juicy tomatoes and delicious winter greens and herbs. Whatever you do, don’t close up the greenhouse after clearing away your summer crops.
After struggling through a summer without a greenhouse, I’m itching to get started in my new custom-built one. This week, I’ll look at the benefits of different types of greenhouses, why I chose mine and how best to prepare one for winter. Next week, I’ll tell you what I’m growing and why these plants work well in winter.
Inevitably, a greenhouse has to fit your space and budget. Bigger ones not only accommodate more plants but, with a larger volume of air, there’s less temperature fluctuation than in a smaller one.
As for building materials, a wellconstructed aluminium greenhouse will last a long time and although recycled plastic is a more environmentally-friendly material, metal is the most practical option. So, slightly reluctantly, we went for a sturdy, white-coated aluminium one.
A free-standing structure lets in more light than a lean-to one, but on the other hand a wall retains some of the day’s heat, so there’s less temperature fluctuation over 24 hours. With our greenhouse leaning against the south-facing wall of the house, we can regulate temperature more easily. Opening a door into the house allows surplus heat to escape from the greenhouse, while a log fire in the house helps warm it in winter. As a bonus, there’s plenty of room for relaxing over a tipple without donating blood to an army of midges.
But don’t despair if you do have a smaller, free-standing greenhouse. The temperature in winter may be up to 5C warmer than outside, so it should provide enough warmth to grow plants such as lettuce, which need much lower temperatures than tomatoes and peppers. And, in all but the harshest winters, the greenhouse is a haven for pelargoniums or blackcurrant sage.
Again, any size of greenhouse protects plants against soggy weather. They’ll cope with cold but can’t handle root, stem and leaf-rotting fungi. And the all-too-common wet-frost-wet scenario is lethal to plants.
Don’t leave the vital spring clean until the season which gives it its name. Do it now. It’s easy for me, with a new, uncontaminated greenhouse, but cleanliness is all, so wash down all staging, shelves and work surfaces, using an environmentally-friendly cleaning fluid. Clean pots and seed trays as this prevents a build-up of pathogens that could cause damping off in spring.
There will be little enough light in the coming months and even though winter salads cope with fairly paltry light levels they need whatever’s available. Light stimulates photosynthesis, which, in turn, encourages strong growth. So thoroughly clean the glass, inside and out, to remove the season’s grime.
Lettuce leaves become pale and thin when deprived of light and this kind of weak plant weighs much less than a healthy one. As a result, it is less able to fight off fungal disorders and is a magnet to any passing pest.
Good air circulation is equally important in winter as in summer. When you control high summer temperatures by opening doors and windows and installing automatic roof vents, you encourage air circulation. But air can become stagnant and damaging to plants during the winter, especially when doors and windows are kept closed to prevent heat loss. So open the door for a couple of hours in the middle of a sunny day.