Agriculture Reference
In-Depth Information
more ground. This absorbs and stores heat during the day, and while a polythene
cover does not insulate as well as glass, a large polytunnel will stay warmer at
night than a small greenhouse. It is this heat retention that makes it possible to
grow food right through the year in a polytunnel.
2 January 2010: a severe cold snap with snow - but despite this bleak appearance, later that
day the temperature in the tunnel was 24°C.
Mark says:
“On 20 December 2009 the temperature outside my polytunnel in Wales at
1pm was 3°C - whereas inside the tunnel it was a whopping 20°C. At midday
on 9 January 2010 the outside temperature was -14°C, while in the tunnel
it was a balmy 18°C. However, polytunnels need sunlight to warm up, so
on a cloudy day the temperature inside will be very much lower.”
Tender plants in a polytunnel will almost certainly need some additional protection
during winter, since frosty weather will still affect them, though not nearly as much
as it affects plants outside. Don't make the mistake of thinking that just because you
have a polytunnel you can grow anything you like for Christmas, because even if
you are one of the very lucky residents of the UK who lives in an area that doesn't
normally get frosts, this just isn't the case. Most of our summer crops depend on
long, bright days as well as warm temperatures, so no matter where you live in the
 
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