Growing Vegetables in a Greenhouse

A small greenhouse, even if it is unheated, affords sufficient protection to start sowing vegetables long before the open ground outside has either started to dry out or lose its winter chill. The combined use of a greenhouse and a row or two of cloches, get the seed germinated and plants ready for transplanting,  It is then possible to bring forward the cropping and harvesting of peas, broad beans runner beans, lettuce, beetroot, cauliflowers, etc.

Germination of such seeds as tomatoes, cucumbers, marrows, peppers, sweet corn, etc., requires an extra level of temperature. Heating the whole greenhouse is expensive, but the problem can be solved by using a Ward propagating frame, large enough to take three half-size and four quarter-size seed trays or eight half-pots. This is electrically heated but economical, the temperature controlled by a thermostat fitted with a small dial at the end of the frame. Just above 60°F (15°C) is the right temperature for most vegetable seeds to achieve good early germination. If heat is not available, however, timing of tender subjects such as tomatoes is important; this should not be earlier than April, otherwise they will suffer a setback on the greenhouse bench after pricking out.

November, is the time to sow lettuce – a couple of seeds in each small peat pot will ensure after germination the strongest seedling can be selected and the surplus discarded. You will also be able to sow Little Marvel peas, a variety full of flavor and sweetness, as well as broad beans (try The Sutton’ instead of the flavorless `Aqueduct’). For a few early cauliflowers ‘All the Year Round’ takes a lot of beating. And runner beans, sown in mid-April, produce strong plants by the end of May or early June, just the right time to plant them out after the last spring frosts. All these and more can be started in small peat pots, which should be thoroughly damped in warm water before being filled with seed compost. Some peat pots (Fyba Pots) come with a trace of fertilizers in the peat, excellent for ensuring robust plants by the time they go outside.

To get the best results from cloches, put them out in a line well in advance of planting, so that the covered soil has time to lose some of its chill and wetness. For lettuce and beetroot, small tent cloches are sufficient, while for peas, beans and cauliflowers, the larger barn cloches will be needed. Because the sun’s warmth is increasing daily, small gaps should be left between each cloche, otherwise the plants may get cooked. The cloches can be removed for periodic surface cultivation, which is good for the plants and for weed control, or for watering during a very dry spring. Most makes of cloches are provided with a pair of ends to prevent the cold winds being tunneled along the row.