Around the turn of the century I was commissioned to design and carry out the fit-out for a new specially designed greenhouse that was part of a Lottery sponsored project. The two-storey greenhouse was a semi-circular shape which faced south, with an air pillow roof, and had banks of windows overlooking a large circular pond. Cooling was via colder air from over the water entering through the lower windows and then rising as it got heated in the greenhouse until exiting through the round windows at the top of the back wall; heating was mainly through geothermal heat exchangers with a gas boiler back-up.
The unique concept about the greenhouse, which I think was what excited the Lottery people enough to offer the grant, was that all the plants had to be grown hydroponically; there was to be no compost or earth at all. The design of the greenhouse and the concept were by Robert Irvine who had created and run the Hydroponicum at Achiltibuie in Scotland. However, early in the project build he had a major disagreement with man who was managing the project at the time and left; I was then offered the contract.
Downstairs, which was to have a Mediterranean climate, I decided to showcase a variety and range of edible plants – lettuces and salad leaves over the winter and heritage tomatoes over the summer. These were to be grown using the nutrient film technique. Seedlings were started in small pots of perlite which were stood in about a couple of centimetres of water containing a weak nutrient solution. When the plants were large enough they were placed in long plastic trays down which nutrient solution was continually pumped via a water pump in a tank at the bottom of the tray. The strength of the nutrient solution could then be increased, or the individual nutrients varied as the plants grew, flowered, and fruited.
The vast majority of tomatoes grown in the UK use this method (or a variation) and I thought it would be interesting for people visiting to learn about that.
The other main method of growing plants hydroponically is to basically grow them in pots but use a soil substitute. Here I used expanded clay pellets to pot up the plant in a specially designed pot (with a lot more holes at the bottom than normal pots, which was then placed inside a decorative (and waterproof) outer pot. The inner plant pot then sat in a layer of water which rose via capillary action up the expanded clay pellets so that the plant roots always had water but never got waterlogged. A small water level indicator fitted by the side of the pot so you could tell easily when the plant needed water.
Although unusual in the UK this method of growing plants is more common in the rest of Europe, particularly for office houseplants.
Coleus, pelargonium, gloxinia and various other houseplants grew well. The above photograph was taken in March when the plants were moved into the new greenhouse.
Upstairs I decided to create the effect of a series of habitats from ranging jungle to desert using a combination of the two hydroponic techniques. The plants were grown in pots with expanded clay pellets and then sat within a large shallow bed that held perhaps three or four centimetres of nutrient solution but all the nutrient solution could be refreshed or circulated via a pump and reservoir placed downstairs.
The large Ficus plants I was able to source from Germany, but for many of the more interesting feature plants I bought in compost, washed it off and then transferred the roots into the clay pellets. Most plants like cocoa, foliage begonias, ginger, Solandra maxima were fine, only a few species sulked and refused to grow.
My banana plantation (7 different varieties) was particularly successful. You can see in the picture above the depth of the bed in which they were growing – there is still some finishing off needed there with tidying the waterproof liner of the bed and the gaps between the plant pots inside the container were later filled with clay pellets.
For the desert section I set the cacti within crushed glass with larger ‘boulders’ of glass to give it a futuristic feel. Cacti are particularly well suited to growing hydroponically – it is easy to keep them dry over the winter and then to regulate the amount of water and food they get during the summer.
The hydroponicum was based at an environmental centre in the north east called Nature’s World. The charity that ran the centre had financial problems for some time, partly as a result of the cost of running their millennium project, and finally went into administration at the beginning of 2013: Middlesbrough council, who own the land, are now looking for someone to run the site.