Most vegetable growers use their greenhouse to produce the standard crops; tomatoes, peppers, cucumbers, aubergine (egg plant), etc. as well as for starting seeds in shelter prior to planting out. There are ways in which your greenhouse can be more productive for you though.

Winter Salads

Lettuce can be quite hardy plants and you can sow Arctic King, Valdor and Winter Density for successional crops through to next season. Spring Onions like White Lisbon Winter Hardy will come on faster as well and if the season is mild, you can bring other varieties along for a very early crop before you need the glasshouse for other crops. Radish will also provide a welcome addition to your winter salads. Since they can be ready as quickly as three weeks from sowing and do not hold for long, you really need to sow successional each week. Sow thinly and you will not need to thin.

Vegetables

Early vegetables will make use of your vacant space before the main season starts and you need the room for tomatoes, peppers etc. If you plant at the edge of the border or pick towards the edge, you will be able to share the space when you plant tomatoes in the centre. As the tomatoes grow, you will have pulled the vegetables and so there will not be any competition.

Carrots

Fresh young carrots always beat stored maincrop for sweetness and these can do very nicely in the greenhouse border. Sow in February using an early variety such as Amsterdam Forcing or Early Nantes pulling alternate fingerlings as they grow as a delicacy.

Beetroot

You can also get an early crop of beetroot by sowing in February. Picked young they will make an early addition to your spring and summer salads.

Potatoes

In January plant some early potatoes, usually 3 in a large pot with a compost mixture. This can be a peat-based compost mixed with John Innes No 3 or peat plus fertiliser or your own mixture, as you prefer. As the foliage develops you top up the compost and should have a nice crop by April. You can also grow in the border but potatoes and tomatoes are the same family so can share disease. Potatoes require a lot of water but you don't want them sitting in water. Ensure the compost is kept moist but try to achieve a balance.

Greenhouse Temperature and Ventilation

These early vegetable crops will do well but you need to ensure the greenhouse is kept frost-free. Insulate with bubble wrap or heatsheets and utilise a heater to keep the temperature a few degrees above freezing in cold spells. Don't forget that, even on cold days, the sun may shine and heat your greenhouse up higher than you wish. An automatic vent opener is invaluable to prevent this. On warmer days you do want to give the greenhouse ventilation or those pests and diseases will have a field day destroying your crops