Bellflowers (campanula) are usually classified as perennials, i. H. they are perennial herbaceous plants that overwinter thanks to their underground rhizomes. However, this does not apply to all types of bluebells, as some are only annual or biennial.
Most bluebell species are perennial
Bluebells keep coming back
As perennials, most types of bluebells develop rhizomes from which the plants sprout anew every year. This has the advantage that the bellflower in question will come back even if its above-ground parts have frozen over the winter. In this case, simply cut down the frozen and dead shoots vigorously, then the fresh ones will have enough space to sprout. However, among the numerous different types of bluebells there are also some that are only one or two years old. At least for the biennial varieties, however, it can be said that these mostly behave like short-lived perennials if they are cut back before the seeds are ripe. This group also includes the popular Marian bellflower.
Perennial bluebells overwinter
Many annuals are also perennials in their homeland, but they regularly freeze to death in our climatic conditions and therefore have to be resown every year. However, you can easily overwinter such specimens under cold house conditions: bluebells need a frost-free environment that is cool and dark at a maximum of 10 °C. Other, quite hardy species, on the other hand, remain in the garden and are only provided with winter protection. It is important to protect the root area in particular, as the plant will sprout from it again. However, if the above-ground parts freeze away, this is not particularly dramatic.
tips and tricks
Remember that annual and biennial bluebells need regular re-seeding. You can also leave this to the plant itself, for example by not cutting off the withered inflorescences. This gives the seeds a chance to self-sow. Of course, you can also collect the ripe seeds, prepare them accordingly and sow them later.