Organic Gardening

From Down Under

Story by John Allen A COGS Member

Margaret has been on my back for a while to build a greenhouse. When we were in Brisbane a few weeks ago (see separate report) we saw a shadehouse built by David Heaton. It was shade cloth clipped onto a frame of semicircles of 2" irrigation pipe, held in place by slipping the ends of the pipes over short star-pickets.

We thought this was a brilliant idea, rather than make a shadehouse we could make a greenhouse using the same design, so on our return to Canberra I built a similar, but larger greenhouse. Our green house is about 2m square and the centre is 2.4m high. The frame comprises three semicircles of 2 inch irrigation pipe which are jammed onto star pickets which protrude about 400mm out of the ground. The outside edge of the centre pipe is at the same level as the inside edge of the two outer pipes - the centre pipe supports the plastic but the plastic is not clipped to it.

Clips for the plastic were made by cutting a piece of the irrigation pipe into sections about 50mm long then cutting a small piece out of each section. I used about 80 clips. To avoid the sharp edges of these clips damaging the plastic, I filed the inside corners a little.

Heavy-duty clear plastic was then clipped to the front & rear pipe frames. First, a single main sheet around the pipes forming the roof and sloping sides - it is important to put this sheet on first and bring the plastic over the centre pipe and under front & rear pipes, wrapping the plastic well around these. A sheet goes onto the back; and then a sheet for either side of the doorway. Due to the curved frame and to maintain a smooth finish, cuts were made in the plastic up to the level of the pipe about 100mm apart.

To stabilise the pipes laterally a single piece of timber joins the front and back pipes (under the plastic) at top-centre. Three other pieces of timber were fixed to form a door-frame. Timber is attached to the plastic pipe using very fine bolts (large holes may make the pipes susceptible to buckling).

The door itself is a double piece of plastic fixed at the top, weighted at the bottom - eyelets and canvas clips are down the sides. A vent, made of plastic, which can be clipped up or down, is above the door.

The unit is stable, but in high wind areas it would be advisable to secure the pipe-ends on the start pickets either with bolts through the pipe and start pickets, or by attaching a chain to buried bricks.

Be careful that the irrigation pipe is not forced too far out of it’s natural shape otherwise it could buckle in strong heat.

We put some shelves in it and the greenhouse is now chock-a-block with seedlings and performing beautifully!

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