many commercial growers of flowers grow in poly tunnels, so no reason why not. you'd have to think about the temperatures the tunnel would get too and the humidity. just think of those plants that like more heat that we have to cosset in the open.
dont know what to suggest though.

I bought a large plastic greenhouse to dry out my plants in pots. Working well but it is not frost free, just a few degree above. It gets very damp even with the door open, so I have to be careful with mould. Come spring the plants are ahead of those outside and are better looking having been out of the worst of the winter.

My only concern is polytunnels are quite ugly, so position it is a place where it causes least offense.

You can grow a lot of things in it, anything that is half-hardy upwards (just remember that it will still freeze inside unless heated but plants are more hardy in dry cold than wet).

If I had a tunnel like that I would leave both ends permanentley open and grow hardy garden plants that I liked.

Would be a super project for slightly tender plants such as Daturas, Callistemon, Phoenix palms, bourgainvillias etc.

My only concern would be ventilation.....poly tunnels are notorious for getting very hot and stuffy in summer and damp in winter...which is a big killer, you'd need a few fans to keep things moving.

Good luck and let us know what you do

Those wonderful displays of plants at Chelsea are only possible because they are grown in huge greenhouses.

you can go virtualy tropical with a polly tunnel . look up urban jungle and see what thy grow . most desserts freeze at night .i know a plat expert who actualy grows cacti outside year in and year out . id say like kildermorie that the tunnel itself is ugly realy .

Hi, thanks to all who commented on my polytunnel idea. Tunnels are indeed unsightly, however mine is well out of sight to the rear of the dwelling. It's going to be a very secluded garden! I hadn't thought about ventilation and it may well be a problem because I've experienced mould on strawberry plants before and didn't know what caused it. I will therefore need to get power supply installed for fans. Bulbaholic makes a good practical, straightforward suggestion and I gave it much consideration. However I'd like this to be a cat free zone. I'm not anti cat but there are quite a lot of them in this locality and I think they would find dry loose soil irresistible on a cold wet day. I will try many of the plants suggested and urban jungle looks like a site where I could spend some time, and money! Thanks again for all your comments and I welcome any more you may think of.

Cats would definitely enjoy the pleasure of a polytunnel, Westerne, but you could make large end doors with a mesh covering to allow the air to pass through freely. With one of our greenhouses I did not fit the glass in the gable end but made wooden frames covered in mesh, then similar for the door.

yourmore than welcome . you can check urban jungle out on the internet too .

that's a good idea Bulbaholic. double doors at one end are solid timber and the single door at the other end has just the upper half wire mesh. possibly a ventilation concern anyhow. So maybe a worthwhile task. Thanks for your help.