The buddleia delights every summer with its long, sweet-smelling flower spikes in strong pink or purple. So that you can enjoy this shrub for many years, you should care for it properly over the winter - some species are not hardy and others are only partially hardy.
Which types of buddleia are hardy?
The hardy buddleia species Buddleja davidii and Buddleja alternifolia can tolerate frosts down to -20 °C, while Buddleja globosa, Buddleja colvillei and Buddleja x weyeriana are sensitive to frost and should overwinter as potted plants. Young plants need frost protection through a layer of mulch.
Which buddleias are hardy - and which are not?
The two species Buddleja davidii and Buddleja alternifolia are probably most commonly found in German gardens, both of which are reasonably hardy and can therefore be planted out in the garden. Due to their rapid growth and sheer size, they are not suitable for pot cultivation, with the exception of some specially cultivated low-growing varieties. Buddleja var. nanhoenensis, which is well suited for the rock garden, is also hardy and can therefore be left outside. Species such as the globe buddleia (Buddleja globosa), the Buddleja colvillei from the Himalayas and the yellow buddleia (Buddleja x weyeriana) are absolutely not hardy and therefore only suitable for pot cultivation, although the latter can be left outside in the wine climate.
Young buddleias need winter protection
However, the hardy species Buddleja davidii and Buddleja alternifolia only become resistant to cold as they get older. From the age of around five years, these buddleias can tolerate frosts down to minus 20 °C. However, when freshly planted and as a young plant, they require light frost protection in the form of a thick layer of mulch, which you apply in autumn. The freezing back of the shoots, on the other hand, is not a big deal, as they are cut back in the spring anyway, at least with B. davidii. The plant then sprouts again.
Overwintering buddleia properly in a pot
You should overwinter buddleia cultivated in pots as frost-free as possible, even if it is a hardy species. Due to the small amount of substrate in the pot, the roots do not receive sufficient protection in severe frosts, but if they freeze back, the entire plant dies. Potted buddleia overwinteres best in a bright and cool place at a maximum of 10 °C. Don't forget to water the plant from time to time, only fertilizing should be stopped from September.
Tip
In contrast to the rest of the plant, the seeds of the buddleia are very robust and can survive temperatures significantly colder than minus 20 °C. The following year you can look forward to numerous young plants despite the harsh winter, which is why it always makes sense to clean out dead shoots.