Alison Swanson celebrates and benefits of a polytunnel

Polyamorous plotting
If growing food on your allotment makes you happy, imagine the extra joy from having a plot with a polytunnel. Even the most basic model generates enough heat to grow a wide range of tender crops from tomatoes to chillies and more exotic treats like cucamelons or achoca. Anyone can achieve this, and the only proviso is access to a water butt or tap. What’s not to love?  

Quick and easy
Every polytunnel needs tomatoes (Solanum lycopersicum). For easy quick gains purchase young plants around March or April, pop in a bed, water regularly and when the flowers emerge feed them tomato food. It’s worth knowing there are two types of plants, either bush or vine. Whilst the former needs no special attention, the latter must be staked, and its side-shoots removed. These are the new shoots which grow between the main stalk and branches. Another way to think of it is to nip out the smallest shoot whenever you see three stalks growing from the same place. Excellent vine tomatoes which are easy to get as plants are ‘Sungold’ and ‘Shirley’, and a good bush type is ‘Cherry Cascade’. Chillies (Capsicum frutescens), bell peppers (Capsicum annum) and aubergines (Solanum melongena) are also good candidates to fill a tunnel productively. Grow these in the same way as bush tomatoes but nip out the topmost leaves, called the growing tip, when they reach between 25 and 30 cm tall. This will secure bigger fruit. For aubergines, the gorgeously shiny ‘Black Beauty’ is commonly available in plant form and Californian Wonder’ is a good bell pepper, also available in most garden centres. Growing directly from plants and plugs however does require some flexibility, you won’t always get the precise variety you want. Do be relaxed however and try whatever plants are available.

Scottish Gardener:

A bit of variety
The big advantage of growing polytunnel crops from seed is the sheer variety available without restriction, and you get to choose. For example, there are thousands of tomatoes you will never see in a garden centre ranging from heirlooms like ‘Stupice’ through to the strangely unusual pink pleated ‘Zapotec’ or ‘Peche vilmorin’, which is genuinely peachy complete with fuzz, but in a good way. Sow the seeds thinly on good compost in trays, cover lightly and always keep moist. When seedlings appear thin these out, leaving a few cms around each, and when they reach around 4-5cm transfer them to small pots to grow on. Plant in their final location directly into the main polytunnel beds when they are around 15cm tall. Success requires sufficient warmth, at around 20˚C, for the seeds to germinate. This is achievable around mid-March onwards and a propagator lid over the seed tray helps.

Taste the exotic
There’s a lot of fun in growing chillies, tomatoes and aubergines but why be constrained when you could also grow sweet ground cherries (Physalis pruinosa) or savoury tomatillos (Physalis ixocarpa) and (Physalis philadelphica) just as easily? Sow and grow them just like tomatoes, except don’t prune and always grow more than two of each to enable pollination and fruit to form. For added interest all types of Physalis grow a protective husk, giving them the look of tomatoes that nature has pre-packaged into tiny paper bags. Home grown tomatillos and ground cherries are still quite unusual, so fewer named varieties are available. Try ‘Golden Berry’ ground cherries and ‘Violet’ tomatillos, or ‘Plaza Latina Giant’.

Scottish Gardener:

A little bit different
Of course, any self-respecting polytunnel-er must also grow cucumbers (Cucumis sativus), cucamelons (Melothria scabra) and achocha (Cyclanthera pedata). Cucamelons resemble small cucumbers and achocha are spiky and slightly weird but interesting to eat. Sow seeds for these climbers in small pots in April or May when the tunnel is warm enough, keep moist and transfer the young plants to the main bed when they have a few leaves. The only things that you absolutely must do is keep them well watered and provide nets or strings for them to grow upwards.

Do you need more convincing?
A polytunnel really is worth the investment but if money is tight you can construct your own. Some truly beautiful versions have been created from bent hazel hoops like a bender. To be on the safe side, always check site rules before building anything but if the committee objects you could always suggest a one way ticket to Bhutan.