Agriculture Reference
In-Depth Information
While potatoes are not generally thought of as tunnel plants, growing them
under cover can give you the earliest harvest of new potatoes you've ever had. In
warm years you can even plan them for your Christmas dinner - but beware, a
sudden frost might change everything!
First early potatoes planted in mid-February should be ready towards the end of
April, a full month before the outdoor plants. If you can save a few of this variety
to act as seed potatoes, they can be planted in the tunnel from late August to give
a harvest at the end of December.
Preparation
Seed potatoes are usually available in gardening shops from late December
onwards, and from your normal seed supplier shortly after that. Potatoes are
described in terms of the time they take to mature, with the longest 'maincrop'
varieties being the best for storage. For tunnel use, you want the fastest-maturing
varieties, which are described as 'first earlies'. For the very earliest harvest the
seed potatoes should be 'chitted' before planting (see Chapter 3, page 31).
Sowing
Potatoes respond well to lots of food as well as the water-holding properties of a
good soil, so dig the earth over well and incorporate plenty of manure or compost.
Never plant potatoes in a spot where they have been grown in the three previous
years. Create trenches about 15cm deep and 40cm apart, with mounds 15cm tall
between them. Place the seed potatoes, chits up, at 25cm intervals along the foot
of the trench, 5-10cm below the surface.
Growing
Potatoes are not hardy and are very prone to frost damage, so they should be well
protected in cold weather. Frost will kill the edges of affected leaves and can easily
kill the entire plant, or at the least seriously set it back. Cover with fleece any
time frost threatens, or you may lose the lot.
Once the plants reach 10-12cm tall, carefully pull the walls of the trenches in and
cover them again. If you do this a couple of times, it results in longer root growth,
which in turn means a bigger and better yield. Eventually, the trench will have
become a ridge, from which the plants will continue to grow. At this stage, wait
until things are starting to cool off at the end of a nice warm day, then put down
a layer of straw on the earth around the potatoes. Every little bit of extra warmth
you can give the plants will help in the cold weather.
Harvesting and storage
When the plant flowers it is an indication that tubers (potatoes) are forming in
the earth beneath, and they can be lifted at any time. Some varieties of potato
don't show flowers, so if no flowers have shown by nine or ten weeks (or if you
