If your summer lilac is drooping, there are a number of things that could be causing this problem. With the solutions listed here, you can get your Buddleja davidii back on track.

Faulty planting

The most common cause of a summer lilac that keeps showing drooping foliage is improper planting. Although the Buddleja davidii is not really demanding, you still have to consider a few points, above all the location and soil. Buddleia should not be placed too dark, cramped or close to other trees. For this reason, solitary planting or a spot in sparse hedges is best for the plant. The location should be as follows so that the leaves of the summer lilac do not hang:

  • Light requirements: sunny to light semi-shade
  • warm
  • sheltered from the wind
  • no north facing
  • Planting distance (perimeter): 100 to 150 cm

Of course, the location is just as important as the soil. Fortunately, the butterfly bush is frugal in this aspect. Neither a specific pH or type is desired. Only wet and compacted soils should be avoided. More suitable are:

  • lean to slightly nutritious
  • locker
  • permeable

If necessary, you can loosen the soil with sand or gravel. If the summer lilac is to be transplanted to improve the location, this should not be done during flowering or a new shoot. Suitable times are:

  • mid-September to October
  • mid-February to mid-April

Cut it back beforehand so that the shrub can grow well. About two thirds is enough. This way you can be sure that it will not be too strenuous for the specimen.

Tip: Buddleja davidii does not like to be together with other trees and plants, but with a wide variety of perennials. For this reason, the plant is often planted as a perennial bed center.


As dangerous as waterlogging can be, the plant should not have to suffer constant drought. Drought stress can show up in downward-facing leaves and flowers of buddleia. Since the lilac should only be watered as needed, it is particularly important to check the location regularly in summer. Use the thumb test for specimens in the bucket. Alternatively, you can water daily according to the following pattern:

  • do not water at lunchtime
  • water as needed
  • Use low-lime water (e.g. rainwater)
  • do not water when it rains
  • optional: create a mulch layer in spring
  • Materials: compost, humus, straw-green waste mixture
  • protects against drying out

nutrient deficiency

Buddleia is not a hungry plant. However, if you failed to give the plant a nitrogen fertilizer in the spring, problems can arise in the summer. The result is hanging leaves and weak growth. You can give the plant a helping hand with a slow-release fertilizer for flowering plants or compost with a little liquid fertilizer, especially for outdoor specimens. Potted plants, on the other hand, are supplied with liquid fertilizer every two weeks during the vegetation period, which is administered via the irrigation water.


A wet location is devastating to the vitality of the plant and should be changed as soon as possible. A reason for this could be constant rainfall, excessive watering, insufficient space, incorrect or compacted soil. Waterlogging can be recognized by the following symptoms:

  • leaves hanging
  • flowers hanging
  • plant weakens
  • Earth smells musty
  • Earth is permanently wet

Waterlogging leads to rotting roots and, in the worst case, to a fungal infection that can spread to the trunk. If this is the case, the buddleia can no longer be saved and must be disposed of. As soon as waterlogging is suspected, you must act quickly and carefully remove the butterfly bush from the ground. Be careful not to damage the roots when removing the root system from the wet substrate. Damaged roots will cause the leaves to droop on the buddleia. For this reason, the root ball is examined for rotten, damaged, dried up or dead roots. Remove them completely and let the roots dry completely. You can then prepare the planting hole in the following way,

  • create drainage
  • Drainagematerial: Kies
  • improve earth
  • Work in sand, compost or gravel

Check the site for dryness over the next few days. Once the top layer has dried, water. At this point, the danger of further waterlogging should have passed. The same procedure is recommended for Buddleia in the tub after the plant has been freed from the substrate:

  • select a larger pot if necessary
  • Pot must have drainage holes
  • fill in fresh substrate
  • Substrate: 1 part soil, 1 part drainage material
  • Soil: Potting soil, potting soil
  • Drainage material: Kies, Blähton
  • Mix the substrate well
  • fill in
  • pot

damage from frost

Don’t underestimate the cold when it comes to Buddleia. Late frosts in particular are dangerous for the plant, since new shoots are already on their way. The following symptoms will tell you in June whether your Buddleja davidii has suffered frost damage over the spring:

  • Leaves curl up
  • hang down
  • then dry out

Late frosts are particularly dangerous for young plants, as they are not yet as robust. Cut the affected shoots back into the healthy wood. The shoots are removed a few millimeters above a healthy leaf sprouting or a bud.

Lack of cutting care

Buddleia must be pruned annually to maintain the vitality of the plant. If one of the two dates in spring or winter is missed, the crown can grow significantly too dense in the following season, which can quickly become a problem. This can lead to drought stress or an increased nutrient deficiency. As a result, drooping leaves can be seen on the summer lilac. Spring pruning is recommended to prevent this problem. You will have to put up with the flowering a little later, but the butterfly bush will be much healthier as a result. The cut is made in the usual way.

Pest: Aphids

Among the most dangerous pests for the buddleia are aphids . The pests rob the crop of a lot of energy and permanently weaken it, resulting in drooping leaves. In most cases, Aphidoidea populate specimens suffering from drought stress. In addition to the weakening leaves, an infestation by the lice can be recognized as follows:

  • leaves turn yellow
  • Identifying lice on the plant
  • plants weaken
  • honeydew visible
  • Ants settle in the immediate vicinity

You can remove the lice daily with a hard jet from the garden hose or you can wipe off the infested shoots and leaves with a household remedy. Use a mixture of one liter of water and 20 to 50 milliliters of soft soap, which you then fill into a spray bottle or apply with a cloth. It is important that you carry out the procedure on a weekly basis to prevent re-infestation. Depending on the intensity of the infestation, you can remove the infested greenery to contain the insect colony immediately.

Pest: Greenhouse whitefly

Like lice, the larvae of the greenhouse whitefly (Trialeurodes vaporariorum) are a problem. The pest is also known as whitefly. She lays her eggs under the leaves, whereupon the larvae hatch and suck on them. As a result, the leaves of the buddleia droop and yellow quickly. In addition, the summer lilac weakens with increasing intensity. Infestation is more common in greenhouses, conservatories and generally enclosed spaces. Check the leaves for the hatchlings and remove them. Further steps are:

  • Hang yellow boards
  • Wipe leaves with soft soap or canola oil solution
  • Remove leaves with eggs and discard
  • Use nematodes or predators such as parasitic wasps (in the greenhouse)
Note: An insect hotel in the garden protects your lilacs from pests, as numerous predators settle there. For these, the larvae of the whitefly and lice are an ideal meal.

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