A Smart Greenhouse
A greenhouse deserves intelligent design. While these spaces can be incredibly productive, many fall short in size, ventilation, and thermal mass. Take, for example, the typical English small shed greenhouse: a single sliding door, a concrete base, and slim grow bags for tomatoes. Such setups often require daily or even twice-daily watering, and overheating plants frequently force the unsightly remedy of whitewashing the glass.
I don't mind hard work, but I avoid unnecessary tasks. It's more efficient in the long run to design and build smartly from the start. Greenhouses can introduce their own set of problems overheating, excessive watering, and pests like insects and rodents that may damage your crops. With tomatoes, which are mostly wind-pollinated, a poorly ventilated greenhouse can become so hot that hand pollination is necessary.
Understanding the common pitfalls is essential before buying or erecting a greenhouse. I recommend a glass, aluminium frame greenhouse for its longevity. While poly tunnels might work in less affluent settings, the plastic degrades over time and ultimately contributes to landfill waste or is incinerated in power stations. Alternatively, free greenhouses are sometimes available locally; though often require disassembly, take photos, their reconstruction becomes much easier once you understand the design.
If you decide to purchase a new greenhouse, opt for one with doors at both ends and ample roof vents. A through draft design not only provides excellent cooling but also improves pollination.
The Solution
An intelligent greenhouse operates as a dynamic system where stocks and flows work in concert. Think of stocks as the reservoirs of resources stored water in the soil, thermal energy held by materials like concrete or water, and accumulated nutrients in the growing medium. Flows, on the other hand, are the movements of these resources: the circulation of air that regulates temperature and humidity, the irrigation that replenishes water stocks, and the flux of energy from sunlight entering through strategically placed vents and windows. By carefully managing both stocks and flows, you create a balanced environment that minimises waste and maximises productivity, ensuring that every resource is used efficiently while maintaining optimal growing conditions.
Our Greenhouse
We require each year; 200 kilos of chopped tomatoes which are reduced down to 100 kilos of rich concentrate., and fresh tomatoes usually available from May to November.
Inside our greenhouse a large raised bed sealed with a liner and filled with animal waste compost to nourish six tomato plants. These plants receive gravity fed irrigation from a stored roof water supply. Excess water and nutrients accumulate in a shallow pond, which the compost absorbs like a sponge, ensuring the plants thrive throughout the season.
The raised bed and foundation wall serve as thermal mass, absorbing warmth on spring and autumn days and radiating it at night to stabilise the temperature. During the hot months, all vents and double doors remain open to maximise ventilation and cooling, while custom fabricated mesh doors keep out rodents, birds, and butterflies.
An efficient operation ensures irrigation coincides with harvesting fresh tomatoes. a tap floods all six plant bases; an inline whistle signals that water is flowing to remind the user. An inspection tube provides a visual check of the wicking water level.
Each plant is supported by a reusable mesh cylinder with large gaps that facilitate easy picking. This design encourages natural growth with minimal stem cutting and provides the essential ventilation needed to inhibit mould.
