It can be difficult if not impossible to grow aubergines outside in much of the UK. A polytunnel, however, makes it possible, even easy, to grow this heat-loving summer crop – even when the summer here leaves something to be desired.
A polytunnel can give aubergines the extra warmth and the humidity that they need to grow and set fruit successfully. They can be grown in the ground, in grow bags or in containers within the polytunnel and will do well in the same conditions as peppers in the polytunnel and can be placed in rotation with other members of the nightshade family such as tomatoes or potatoes. Cucumbers also like similar conditions. French beans and peas can also be good companions for aubergines, as can herbs such as thyme and basil.
While aubergines can grow happily in a polytunnel, the seeds are best sown inside as they will need to be started early in the year – in either February or March – and require a high temperature for germination. Either a warm location indoors or a heated propagator will be required and seeds will germinate in 2-3 weeks. Water sparingly but be sure to keep the soil moist during this time.
Grow your aubergines in 9cm pots or similar initially and then when the roots fill those pots, transfer to larger containers. You can transfer aubergines to a heated polytunnel in April or to an unheated polytunnel in May, after all risk of frost has passed and the polytunnel has warmed up considerably.
If you are planting in a grow bag then you can place three aubergine plants per bag, one plant per container of around 30cm in diameter. In the soil, a spacing of 60cm between plants is usually recommended. It is a good idea to tie in growing aubergine plants to a support as they grow. When the plant has reached around 30cm in height, nip off the growing tip of the main stem.
You should be sure to water aubergines regularly and to feed them with a high potassium organic feed every couple of weeks once the first fruit has set. (Banana skins placed beneath the plants can also help with potassium needs.) Mist the foliage with tepid water at least twice a day to discourage red spider mite and to help encourage the fruits to set.
It is important not to leave it too long before harvesting your aubergines. Make sure you cut them when they are still shiny, around 15cm in length. Once fruits have dulled they become bitter. The harvest should come between late July and September.
Outdoor crop – sow inside March.
Plant out under protection May.
Indoor crop – sow inside February – plant inside April to May.
Picking time – July to September.