If you’re new to polytunnel gardening spring can sneak up on you. After all, growth is still slow: it’s not like summer where you have to wrap four-inch cucumber and melon shoots around their supports every other day. But miss the signs and you’ll lose some of the advantages of overwintering your plants, because things are starting to get a little crowded and the soil is beginning to dry out faster. This can encourage plants like rocket and broccoli raab to bolt, making them tough and bitter weeks before their time.
“Today (18th Feb) marked the end of winter in my polytunnel here in Dorset, and to tell the truth I’m a little sad. I’m a lazy gardener, you see: the winter tunnel suits me nicely because it’s basically a big walk-in larder. Asides from frost protection and very occasional watering, there’s nothing much to do – and I’m very fond of winter salads. But yesterday the first daffodils opened up not far from the house, and I knew it was time to check on the polytunnel.”
Signs of polytunnel spring
Growth is picking up again. Not easy to spot directly, but you’ll notice that plants that were previously well spaced are starting to look a little crowded. This leads to…
Slug damage. It’s too soon to start slug patrol in the evenings, but you can still check your slug hotspots and catch the little bleeders at it. In my tunnel this means round the base of bunching plants like coriander, and anywhere where leaves are hugging the ground. Leave slugs alone at your peril – it’s much easier to eject one slug now than deal with twenty to thirty 2mm hatchlings at the end of March.
Wilting. If plants are taking longer than previously to perk up again after a frost, it probably means that moisture levels in the soil are dropping. Don’t be tempted to drench everything with a hosepipe just yet, as waterlogging can be a serious problem in winter – just increase the frequency of your watering, and be prepared to keep doing this until things warm up enough to reconnect your irrigation system for the spring.
Jobs for very early spring in the polytunnel
Weeding. Growth slows down in the polytunnel over the winter, but some weed species such as grasses and thistles will continue to grow very slowly. Take a good look around the tunnel and nail every weed that you see – it’s so much less work now than when things warm up!
Removing crowded growth. During the winter you will have held back from picking old, ratty leaves because all the plants needed all the solar energy that they could get. But plants that looked well-spaced last month are now meeting in the middle, providing a nice moist canopy that slugs just love. Pick all this tatty lower growth – in the case of salad plants that’s basically everything that you wouldn’t put on your plate.
Watering more. It’s not a bad idea to check your irrigation system now, too: don’t wait until you need it, just in case you have to order new seals or timers.
Cleaning the cover. In the coming weeks the tunnel will need to capture all of the scarce sunlight that it can, so wait for a mild day and get all that green algae off. The easiest way to do this thoroughly is to ‘floss’ with rope and an old sheet.
Get planting. It may be cold, but as soon as the risk of frost begins to recede you can plant a few first early potatoes: give them some frost protection and you could be eating your first new potatoes by the end of April. There’s also plenty you can be planting on a sunny windowsill indoors, such as hardy lettuce and rocket, peas and broad beans in biodegradable pots. If you own a heated propagator you can even crack on with tomatoes, chillies and sweet peppers. Summer’s coming!