Garden Pictures Chat Corner

I would like to overwinter some plants in polytunnels this year due to lack of space.

Why? There are annuals, which die in frost or because they are not suitable for a second year here, and there are frost-hardy ones, of which you will have something next year even without foil (very simplified). The former can be freshly sown from seed if you want to save money. Foils are unnecessary for mature plants and are usually used when you want to protect already pre-grown seedlings (vegetables or also from your sowing) outside from night frosts. In the background of the first one there should be Euonymus, which is winter-hardy. I also cannot identify the other plant in front ... is that a small rhododendron? Or faded viburnum? It seems to me that they were planted together in a pot tray once. I would plant the two with a 50 cm distance so that they have space for themselves. Regarding the other pictures, I agree with and also advise you to plant regionally proven and adapted perennials and then fill gaps with annuals that focus on blooming and not overwintering.

some lilacs and a few berries in pots

They belong in the bed and are winter-hardy. Can work well in pots, but doesn't have to. You don't actually need a green thumb if you read up and look things up.

For number one, I would have guessed a small rhododendron. It should be hardy.

You have annual plants
Plants that already need to be brought inside at around 8 degrees
Some can stay outside down to about 0 degrees
Conditionally hardy means up to hardiness zone 8/7. They need coverings in winter.
Hardy means anything from 7/6 and lower.
For me, maybe 1 in 5 plants survives the winter. Either too warm or too cold. Too dark or too light.

In a pot, the hardiest plant breaks as soon as it freezes through.
In the open ground, lilac and berries are hardy.
Plant the lilac and the berries in the garden. That's still possible.

People, thanks for the presumably well-intentioned advice, but please read again.

The question was: Can I generally overwinter plants in the polytunnel or does the temperature change from sunny=warm to dull/dark=freezing bother them.

I still have everything in pots because the garden is still [KOMPLETT] being dug up.
And in the pots, most of it is simply not winter-hardy, even if it will be later in the open ground.

I am NOT talking about the plants in the pictures.
Nevertheless: The first one is a shrubby speedwell, it is just one plant from a pot.

Why did you then upload the pictures?

Folientunnel will not work for many plants because it is too cold and spider mites and others will probably feel comfortable there.
The measures you need to take depend on the winter hardiness of your plants.

Because this is supposed to be a picture thread...

To put it simply again: Can I overwinter ONE lilac in ONE pot in ONE polytunnel?

These things are always touted for overwintering, but in my experience it is too fluctuatingly warm in such a greenhouse and I imagine a "dormancy" for plants rather with CONSTANT, cool, but not frosty temperatures.

A lilac does not need a plastic tunnel. On the contrary, I fear that it is one of the plants that really suffers there. Place the pots on styrofoam or wood against a sheltered house wall. If it gets really cold, so that you have to fear that the pot will freeze through, cover the pot (there are thick round coconut mats, for example) and wrap the pot. You can also use the branches from the Christmas tree to cover it.