Agriculture Reference
In-Depth Information
CHAPTER FOUR
Spring
Recognising tunnel spring
Polytunnel spring tends to creep up on new tunnel gardeners, largely because it
begins to happen before things really get going outside. By the middle of
February the days are already 90 minutes longer than at midwinter, and they're
getting brighter too. Even though it's still perishing outside, the polytunnel soil
is warming steadily, so don't get caught out. By the time the first snowdrops
appear, growth in the tunnel will already have started and you'll be bringing
your first indoor and propagator sowings out into the tunnel in no time.
Tip
Quarantining new plants
When you bring any plant into the garden from outside, there is always a risk of
introducing disease. To be as sure as possible about the health of incoming plants,
it is a good idea to quarantine them in a greenhouse or cold frame, or on a sunny
windowsill, for a couple of weeks. Take them into the polytunnel only once you are
sure they are healthy.
Despite the increasing warmth inside the polytunnel, however, it is very easy to
let your guard down too soon, lulled into a false sense of security by a few days
of sunny weather. Cold snaps can still strike, so don't put away the fleece just
yet: keep it to hand in the tunnel and watch the weather like a hawk. When the
first seedlings come out on to the staging they will need some protection too.
Make sure that you open the tunnel as early in the day as you can, to let the cold
night air out, and close things up at least an hour before sunset to retain as much
heat as possible.
As the soil temperature increases you'll notice a real difference in how quickly
the surface dries out, especially if you are growing in sandy soil. Once the inside
of the tunnel warms up properly, the amount of water needed increases quite
dramatically and the young growth inside is very vulnerable to dryness. Even if
it doesn't get to the point of wilting, a lot of it will bolt. Although it's tempting to
hook up any automatic irrigation early, be aware that a single savage frost could
do some real damage. A burst pipe in the tunnel can be absolutely heartbreaking.
