If you’re thinking of putting in a polytunnel here are some tips on how to plan everything – including filling it with your first plants. Don’t just jump in! There are some important decisions to be made that could affect the environment inside for some time to come.
The chances are, given that everything usually takes longer than we expect, if you planned on putting up a new polytunnel in time for the growing season you probably ended up being slightly late. Putting up a new polytunnel is a lot of work and if you’ve never done it before it’s hard to estimate accurately. The cover, for example, should NOT be put up on a windy day – unless you like flying huge kites…
Once it’s up, you have a new and quite wonderful gardening space that can give you years of extended growing seasons and delicious crops. But first, you have to create the beds.
Preparing these takes yet more time as well as a great deal of effort. And, unless you’re in the happy position of delegating this to someone else, it will have fallen on your shoulders. So the big question really is, do you prepare the beds before or after putting up the tunnel?
Planning your polytunnel
Whether you actually construct them or not, at least plan the beds first. Don’t leave this extremely important step until the tunnel is actually up! But, it may not be practical to actually finish creating the beds before the tunnel goes over them. Raised beds, especially, might be a serious obstacle when putting up the tunnel – and you really don’t want to trip over them when you’re carrying a heavy hoop section. For instance, if a raised bed occupies the central space, remember that in order to fasten the ridge to the hoops you’ll need to be standing on a stepladder – and it’s not easy to position this on top of a raised bed!
However, if you think you can deal with this, then definitely put the beds in first. Otherwise, at least remove all the turf (unless it’s been very wet and the result will be a quagmire) as by doing so you’ll also remove many of the pests that will otherwise be left inside. You can also clear weeds and undergrowth away from the tunnel wall area, difficult (and risky!) to do once the cover is in place.
Compost and manure
Digging compost / manure / soil amendments into the beds is, obviously enough, a great idea – and it’s much easier to do when the whole area isn’t enclosed by the cover: wheelbarrow access isn’t restricted, and you don’t have to worry about getting too close to the walls while wielding a spade or fork.
Polytunnel space is far too valuable to waste and should be used efficiently. No matter how big the tunnel, next season (or next week!) you’ll wish it was bigger still. However, don’t make the mistake of thinking that a space 25cms wide alongside the tunnel wall will be enough to allow you access to that side of the beds, because it won’t. The tunnel wall will typically begin to curve inwards roughly a meter off the ground, and a good rule of thumb for every path in the tunnel is that you should be able to walk along it pushing a loaded wheelbarrow without having to bend double in the process.
Many people prefer to grow in raised beds, and these are an excellent tunnel option: they’re not compacted through the use of adjacent paths and, being higher, they’re more accessible. Just don’t make the mistake of using the tunnel cover as one of the ‘retaining’ walls of a raised bed, because while strong it’s not made for that kind of stress.
Time your seedlings
Ideally, seedlings should have been started elsewhere (on a well-lit windowsill and / or in a cold frame) roughly a month before you expect the tunnel to be ready. If you timed this right, you’ll have lots of plants ready to go into the waiting beds. If not, all your work just sits there while you wait for the seedlings to grow – what a waste!
White plastic labels, written on and stuck into the pot, are commonly used to identify seedlings. These can be used over and over again, but each time you have to remove the writing from the previous planting. Fortunately, this is easy: rub with a bit of wet earth between your finger and thumb, and the writing will vanish – so long as you used a soft pencil in the first place! Give them a wipe to remove the mud, let them dry and they’re good as new.
Sowing seeds usually takes far less time than everything else, as everything is on such a small scale. Once plants are established, weeding, pruning, clearing excess growth, setting up watering systems and tying up etc take far more time.
Don’t forget to allow some space for staging, or you won’t have anywhere to fill pots, sow seeds, mix soil media, store tools and nurture seedlings. Staging is an essential part of a polytunnel, and there are some great kits available – or, you can make your own.
If there’s enough room, a comfy folding chair isn’t a bad idea either, so you have somewhere to sit after a hard day’s work or a cosy spot in which to ride out sudden downpour. Believe me, you’ll really appreciate your polytunnel when it’s bucketing down outside!