Pink, violet, white, blue and even yellow - the popular summer lilac delights the viewer with its summer blooms. However, not all species and varieties of this perennial flowering shrub are hardy - so if you want to enjoy it for many years, you should know if and what to do - and which varieties are most likely to survive a cold winter.
Buddleja davidii is hardy down to -20°C
Which species of summer lilac are hardy?
Probably the most commonly planted species are Buddleja davidii and Buddleja alternifolia, both of which are hardy after a certain period of time at the location and tolerate temperatures of down to minus 20 °C. This applies to almost all varieties of the species mentioned, but only from an age of around five years. However, freshly planted and younger specimens need light winter protection. On the other hand, rarer species such as the globe summer lilac (Buddleja globosa), the Buddleja colvillei from the Himalayas and the yellow summer lilac (Buddleja x weyeriana) are not hardy at all. This summer lilac should only be cultivated in tubs, planted out in the garden they freeze and - in contrast to Buddleja davidii and alternifolia - do not sprout again.
The most beautiful hardy varieties of Buddleja davidii
You can plant the following hardy varieties of Buddleja davidii in the garden without worrying:
- 'African Queen' with its beautiful purple to violet-blue, very slender panicles
- 'Black Knight', very profusely flowering with crimson to dark violet flowers
- 'Dart's Ornamental White', one of the most beautiful white flowering varieties
- 'Empire Blue' with distinctive light purple flowers
- 'Ile de France' with probably the darkest flower colour
- 'Purple Emperor' with very dark purple flowers
- 'Pink Delight' with beautiful silvery pink flowers
With all the varieties mentioned (although the list is of course not complete, because Buddleja davidii is very rich in the most diverse variants), the shoots can freeze back in winter. However, that is no reason to panic, then after a pruning in spring the shrub will sprout again from the roots. It is therefore important that you protect the roots from frost, for example by mulching the root area.
tips
Even if the selected variety is considered hardy, you should still overwinter it frost-free in a pot culture - here the plant does not have the opportunity to counteract the freezing temperatures.