Heart of glass: Anna Pavord finally has her own greenhouse
Saturday 09 January 2010
For years, I've been doodling greenhouses: lean-to greenhouses, three-quarter span greenhouses, free-standing greenhouses, greenhouses set up entirely for growing a peach or a nectarine, or tailored to bring on flowers for the house, or to extend the season for salads and tomatoes. Now, after a lifetime of doodling, I finally have the real thing and I'm dazed with delight.
It started with a disaster, when during a gale some sheets of corrugated Perspex blew off the roof of the long, south-facing wooden building that the previous owners of our house used as a studio. Standing in this space (roughly 4m wide by 2.65m long) with half the roof gone, I realised how light it was and, facing south and west, how ideally placed for keeping plants warm in winter.
The doodles started to get more serious. The north wall of the building was all concrete block. That could stay just as it was. So could the blocks (covered outside in timber cladding) that went half-way up the walls on the south and west sides. We could glaze the top half of those two walls and put glass rather than corrugated Perspex back on the roof. The existing inside wall, facing west, would be a perfect place to grow a fan-trained peach or nectarine.
So the greenhouse evolved from what was already in place, its dimensions set and to a great extent, its functions also. I've got more and more interested in growing plants in pots to bring into the house, but have been hampered until now by having few places to keep them while they are revving up for their performance. The south-facing side of this new space would be an ideal holding ground for potted plants.
I'd need a bit of a workbench too, I thought, though seed sowing, and general pottering of that nature would still go on in the workshop, at the opposite end of the same studio building. The solid block wall on the north side was the obvious place for a bench in the greenhouse, with a shelf above, right up against the glass roof, where I could put seedlings and cuttings to grow on without getting leggy. I'd spent years thinking about this space. When it all began to crystallise around me, I was pretty clear about the priorities, about what I wanted to do in it.
Since the whole long studio building is timber-clad, it was obvious that the framework of the greenhouse should be wood too. Hardwood or softwood? Time to call Colin, who has a unique ability to translate sketches on envelopes into buildings that work. He priced up the wood and although hardwood (cedar) was outrageously expensive, that's what we decided to get, on the basis that it would last a long time. Colin, who takes infinite care to get things right, shaped all the timber in his own workshop: strong uprights for the south- and west-facing sides, new beams for the roof (the old ones were riddled with woodworm), double doors to open out on the west side.
Ventilation, I knew, would be one of the most important things to get right. Everything I've read about greenhouses (and heard from those who own them) stresses that you've got to have plenty of air blowing through them. We think more, perhaps, about the business of heating them in winter, but even in our iffy summers, greenhouses can get hot. Stagnant air encourages disease. You've got to keep it moving.
So, on my sketch, the south-facing side of the new greenhouse was effectively all window, three of them, hinged at the top and held open when necessary, with old-fashioned stick fasteners. The double doors, opened and pinned back against the walls either side, would take care of ventilation on the west side. Breezes here come mostly from the south-west, so there'd be a good through-draught.
For the roof, I bought three Bayliss Autovents Mk 7 (£35.95 each), two for the south-facing slope of the roof, one for the north. They came via Two Wests and Elliott's extraordinary catalogue, 115 pages of things for a greenhouse, which for years I've read avidly as a kind of fix, a substitute for the real thing.
The vent area (says the catalogue) should be equal to a fifth of the floor area. Ours don't quite match that, but ventilation on the two sides is better than in most, so I reckoned three vents in the roof, each 80 x 80cm, would suffice. What you get is not the window vent itself (Colin made those) but a kind of hinged arm, to open and close it automatically. It works by way of a wax cylinder in the arm; as it heats up the wax expands, pushing the vent open; as it cools, it contracts. Excellent. I don't have to worry about plants cooking in my absence.
The glass in the roof as well as the south and west walls was to be held in vertical glazing bars roughly 215mm apart. The bars needed to be as narrow as possible, which was another good reason for using seasoned hardwood. It wouldn't warp. But how were we going to fix the glass? Should they be single sheets running from top to bottom? Should we introduce horizontal glazing bars? Or should the glass be fixed in overlapping panes?
At this point, I had a vision of fish-scale panes, cut with semicircular ends. You still see these kind of panes in old glasshouses, made not because they look good (which they do) but because the rounded end encourages water to run down the centre of each pane, rather than down the edges. Less leaks perhaps. A longer life for the wood.
The local glass cutter said there was a factory that cut glass like this, but that it would take three months or more before ours could be done. So Colin got all the glass cut to fit, then finished off the rounded ends himself. It took a long time and was an expensive option. Worth it though. I'm happy to live in hand-me-down jerseys for the next 10 years, in order to have those panes.
The rest of what happened was set-dressing. On three block pillars along the sunny south side of the greenhouse Colin set up a lead pig-salting trough 185cm long x 70cm wide. It came from a local junk yard (£80) and is now holding Haemanthus albiflos, veltheimia, pancratium, 14 pots of hippeastrum, 3 big pots of Ornithogalum arabicum, 5 pots of freesias and two tubs of cymbidium orchids.
Outside, we used Lindab's beautiful galvanised steel gutter and downpipe to channel rainwater into a galvanised trough. Lindab is a Swedish company and they make the guttering 100cm, 125cm, 150cm and 190cm wide. We've got the 150cm, with push-on end-stops and snap-on clips. It's beautiful stuff and unlike plastic, it doesn't fade, crack, expand or contract. The trough, for watering plants in the greenhouse, is set just to the right of the door and is 88cm long x 46cm wide x 40cm deep. It came from our local agricultural supplier and cost £77.52. The next thing in my sights is the peach or nectarine to set on that west-facing wall.
Two Wests & Elliott: 01246 451077, twowests.co.uk. Lindab's building products and suppliers: 0121 585 2780, lindab.co.uk
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