There are many different types and cultivars of bluebells (campanula), but not all of them are hardy. Native bellflowers such as the meadow bellflower or the Marian bellflower are particularly suitable for cultivation in the garden. All other species need winter protection outdoors.
You can protect bluebells from frost with some mulch or fir branches
Hibernation depends on the species
In particular, the bluebells native to the Mediterranean countries do not tolerate frosty temperatures well and should therefore be provided with appropriate winter protection in winter. This can consist of a thick layer of fir or spruce branches, for example. However, some actually perennial or naturally annual varieties do not need to be overwintered because they can be sown again every year. Potted bluebells, on the other hand, should always hibernate frost-free, but cool and dark. Ideally, the temperature should not exceed 10 °C. If the winter is mild, the balcony bellflowers can also be hibernated outside, but should be brought indoors as soon as the temperatures fall well below 0 °C.
tips and tricks
If you have no possibility to spend the winter indoors (e.g. a sufficiently cool room). then place the tub bluebells on a piece of styrofoam and place them against a warm wall. You can also wrap the bucket and plant in a warming material (e.g. bast mats).