The wonder of growing in polytunnels
My first “Tunnel Vision” was at Christmas 1984 when we visited the Smiths in the hills around Ballydehob, who grew vegetables in polytunnels. Probably the only other polytunnels at the time existed at the other end of the country at Eden Plants in Rossinver in Co. Leitrim as we would find out a few months later.
When we then arrived in Ireland in the summer of 1985 we had to build our first polytunnel ourselves, because there wasn’t one to buy. Now you see them everywhere and for very good reasons too.
Why grow in a polytunnel?
Do you love tomatoes, basil, sweetcorn and cucumbers? Would you like to be eating your first crop of new potaoes as early as June? Do you want lettuce throughout the winter? If the answer to those questions is yes then the only option in the West of Ireland is to invest in a polytunnel! Polytunnels are an excellent way of increasing productivity at a low cost. The use of it as a growing area brings important benefits:
For growing tender vegetables which require higher temperatures than normally exist in an Irish summer, e.g. tomatoes,peppers, aubergines, cucumbers, basil, sweetcorn.
For extending the growing season, both in the spring and autumn. Examples: carrots, calabrese, celery, courgette, beetroot, scallions, radish and annual herbs such as dill and coriander.
For winter cropping. In a polytunnel fresh salad leaves can be harvested all through the winter. Suitable crops: winter purslane, mizuna, salad rocket, Tat soi, radicchio and Lambs Lettuce.
For plant propagation. Polytunnels can successfully be used for raising plants either on heated benches or even in the soil for bare-root transplant raising.
Another advantage is that a tunnel will allow rather more comfortable conditions for the person gardening or growing during periods of rain.
Here are some ideal crops for a Polytunnel:
Beans/Climbing French
Climbing French Beans are an excellent polytunnel crop. They rarely do well outside unless you have a very sheltered garden. Seeds can be started in small pots or sown in situ if the soil temperature is above 10ºc (53ºf). Sowings can be made from March unitl early summer for cropping from late June until late Autumn. Seeds should be sown about 5cm and 15cm (6”).
Cucumbers
Another prolific crop for the polytunnel. One plant can produce enough cucumbers for a family over the summer. Sow April in seed trays. 24-25ºc. Maintain minimum 15ºc. Pot on when leaves have expanded. Grow in a raised bed in single rows with 45cm (18”) spacing. Plant from early May on. Train up a crop wire.
Tomatoes
Possibly the most popular under cover crop.Sow mid March to Mid April with temp of 20-24ºc in seed trays. Pot on once plant has developed a 2nd set of leaves. After germination maintain min. temp 15ºc. Beds must have a rich supply of organic matter in the form of well rotted farmyard manure or compost. Potassium is very important for tomatoes and may be supplied using seaweed meal or dust. Plant in double rows with 50cm (20”) between rows and 60cm (2ft) between plants.
Other suitable crops include Basil which really thrives in the warm protected environment. Chilli and sweet peppers both grow well in a tunnel. Lettuces take up little space and can be harvested as early as April. Sweetcorn takes up a lot of room but is worth it for the flavour of those freshly picked cobs. If you grow potatoes in a tunnel you could be tucking into your first batch of new potaoes as early as late May/early June.
Warning: Don’t buy a small tunnel! The benefits will become obvious very quickly and you will become addicted. A good size family tunnel is about 12 to 15 meters long.
Inspiration: On a recent visit to Clare I met organic pioneer Jim Cronin at his market stall in Killaloo on a Sunday morning. Despite subzero temperatus all week he had great lettuces and spinach for sale. “It’s called Winter harvesting” he tells me. “The secret is cold-hardy varieties of vegetables, succession planting and double protected cultivation. I had 4 layers of vlies on top of the plants in the polytunnel.”