John Gardiner’s Greenhouse

Visit and build

After several days of glorious weather, the day of the visit had rain forecast, and true to form, just after 2pm the rain descended, which put paid to the plans for a social gathering outside, with more external views of the custom built greenhouse.

The greenhouse was built in 2004 after demolishing an old concrete sectional garage. Thankfully the garage had an electric supply which was straightforward to reuse. The garage had a concrete base which was a more than useful start; however it did restrict the size that the greenhouse could occupy. Hindsight dictates that I should have built it bigger of course…

Many of you will be unaware that my father was a Market Gardener, and that was where my early horticultural talents were honed to a fine degree. Greenhouse building was an ongoing part of the business, so it wasn’t a difficult undertaking to set about home design and construction. There are a several things to take into consideration of course such as which bits should overlap, and then it is pencil, paper and a large tape measure together with an internal wall measurement for my builder to construct the walls (that and the electrics were the only bits contracted out).

I had acquired a large greenhouse many years ago at a sale at a real bargain price, and this provided the wood and spars that were to be used. The design was to construct with brick walls up to the bench level, and then triple wall polycarbonate panels above. The size of the polycarbonate panels were the key to the size at 1.05m wide and allowing for expansion room etc allowed 5 panels to fit the length of the base with a few inches to spare. The width was also calculated according to the length of the panels together with the angle of the roofing irons that I already had. This worked out at just less than 2m for each slope and with the side panels at 1m allowed perfect use of the 4m long polycarbonate sheets. Once again the width fitted the base with just a few inches to spare.

The greenhouse came together over 4 weekends, and with a bit of evening painting was ready for the summer of 2004, just 6 months after we had moved in. The floor was sealed with a bit of concrete around the edges, and with the gentle slope in my favour allows the floor to be permanently partially flooded to maintain humidity even on hot days when the window and door is open. The benches were constructed on site as wooden slatted ones, and are 1 long side bench wide enough to reach across, with others fitting around it to maximise bench size without compromising on reaching to the back. Consequently it looks a bit odd, but the width is too wide for 2 side benches, but not wide enough for a central one as well (something to bear in mind for future building projects).

The iron strengthening pillars were drilled along the top allowing wires to be run the length of the greenhouse so that internal shading can be easily slid into place, and this is usually put on in early March to prevent scorching (the greenhouse runs directly east/west), and removed in October. An external layer is used in spring/summer to protect from excess heat. This does actually make it dull on certain miserable days, but still bright enough for the slippers that I mainly grow. This year I have abandoned the inner shading on the north side to try and get some extra light inside, and am considering removing a bit more just for those plants that need additional light such as the multifloral Paphs and Cattleyas.

Being close to the house, the greenhouse gets used for a variety of things – tins of paint, the mop & bucket, as well as the compost and empty plant pots. An extra shelf was built last year to hold a few more plants. At the time of the visit many of the cooler growing plants such as the Odonts and Cymbidiums were outside, and a decent spring clean made the greenhouse look a lot tidier than usual (see back page), but it soon returned to normal afterwards.

Is the greenhouse perfect, and does what I want? Nearly I would say. One major flaw is that it is all the same temperature zone meaning that some things don’t do as well as I would like them to. And of course it isn’t big enough. It is heated by electric fan which is expensive to run compared to a gas boiler. In reality it works well for me and is just about maintenance free. There’s now a few year’s worth of algae on the roof which needs cleaning this autumn for a bit more light.

Altogether about 24 members made the trip ‘up north’, and most appeared to have enjoyed the experience, especially with a healthy buffet on offer as well. JG