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Buddleia are perennial ornamental plants that are actually hardy. Nevertheless, it can happen that they show frost damage after a hard winter. This is what you should do when the summer lilac has frozen.

In a nutshell

  • Pay attention to winter hardiness when buying
  • Frost protection necessary for young and newly planted shrubs
  • Pruning and patience as rescue measures for frost damage

Buddleia

Summer lilacs, also known as butterfly bushes, are a genus of plants from the figwort family (Scrophulariaceae). The genus is now attributed to over 100 species. In domestic gardens and parks are the

  • Butterfly bush (Buddleja davidii) and the
  • Summer lilac (Buddleja alternifolia)

most widespread. There are numerous varieties of both types, which differ not only in growth and/or flower color, but also in terms of frost hardiness. That's why you should pay attention to whether the selected Buddleja variety is actually hardy in your region when you buy it.

Buddleja davidii 'Nanho Blue' is not only decorative, but also withstands temperatures down to -20°C.
Source: Ptelea, Buddleja davidii 'Nanho Blue', Adapted from Plantopedia, CC BY-SA 3.0

Save Buddleia

If the buddleia freezes, the rescue measures consist of two steps:

  • Determine the extent of frost damage
  • repair damage

Determine the extent of frost damage

The main purpose of this step is to find out whether

  • only the aerial parts of the plant or
  • also the roots

have suffered from frost and cold. If the former is the case, the gardener speaks of the buddleia freezing back, if the latter occurs, the ornamental shrub has frozen and you have to reckon with a total failure.

Freeze back

Frost damage to the parts of the plant above ground always occurs in the summer lilac when it gets too cold for it.

This weather can freeze the butterfly bush:

  • severe winter
  • mild winter with a cold onset of winter in early spring
  • unexpected late frost with very low temperatures

total failure

Fortunately, the roots of summer lilac rarely freeze. danger looms

  • during longer periods of frost around minus 20 degrees Celsius
  • during cold periods (cold periods without protective snow cover)

vitality test

The weather is a good indicator for assessing frost damage, but you should do a so-called vitality test for a precise determination. To do this, scrape off a little bark from the branch with a sharp and disinfected knife. Is the underlying tissue

  • green, the shoot is still alive
  • brown, he is frozen to death

Notice: Only remove as much bark as necessary, as exposing the tissue will injure the plant.

repair damage

In order for your summer lilac to get fit again, it needs a pruning. Proceed as follows:

  • Shorten living (green) shoots to 30 to 50 centimeters
  • Cut off frozen (brown) branches at the base

When you do the pruning depends on the cause and the weather conditions in your area:

  • after a severe winter (rough locations): late March / early April
  • in mild regions: possible from the end of February
  • after a late frost, when no more are to be expected: as soon as the weather is appropriate for the season

Post-pruning care

In order for your summer lilac to recover after the winter cold and pruning, it needs a lot of strength and energy. Therefore, after cutting, spoil it as follows:

  • fertilize with a generous helping of horn shavings and compost
  • Work fertilizer into the surface of the root disc
  • pour

prevent frost damage

Buddleia are generally considered to be hardy. However, they need a certain amount of time to develop their frost hardiness. So are varietal

  • young specimens (less than five years old) and
  • freshly planted older shrubs (less than five years old)

endangered. In order for these butterfly bushes to survive the winter well, you should protect the lower area from frost and cold. The following are suitable as antifreeze:

  • a layer of mulch
  • a layer of compost
  • fir branches
Bark mulch is a good winter protection for butterfly bushes.

Notice: If mild days alternate with frosty nights in early spring, you can cover younger summer lilacs with a plant protection fleece at night.

frequently asked Questions

When should I clear in the event of a total failure?

In the event of a total failure due to frost, you should not immediately give up hope. Wait until mid to late June before digging. With a bit of luck, the summer lilac will still sprout at this late point in time.

Which hardiness zone do summer lilacs belong to?

Depending on the variety, butterfly bushes are assigned to hardiness zone (WHZ) 5, 6 or 7. In the best case, they tolerate temperatures down to minus 28 degrees Celsius (WHZ 5). WHZ 7 varieties, on the other hand, only withstand temperatures down to minus 17 degrees Celsius. However, this information is only intended as a guide, since the microclimate is decisive for summer lilac.

Which summer lilacs are particularly hardy?

Buddleja varieties that show little winter damage are for example
- Bonnie
- Les Kneale
- Nanho Blue
- Nike
- Sunkissed
- White Wings

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Category:

Garden plants