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Buddleja davidii purple flowers


Buddleja davidii (sometimes called Butterfly Bush) was introduced to Britain in the 19th century as a perennial shrub. Today it is commonly found growing on dry, open sites such as brownfield sites, railway embankments and old quarries. It can also exploit cracks to grow out of walls and other structures in the urban environment.


Buddleja davidii plants flower after 2 years. They produce tiny purple flowers in a long, pyramidal shaped clusters 15-20 cm in length. These are produced through summer to late autumn, followed by seed setting. It has long, arching, woody branches reaching 5m in height, growing between 0.5 to 2m per year, and shallow, fibrous roots.


Vigorous growth of Buddleja davidii outcompetes native plants and can form dense stands which block out sunlight causing biodiversity issues. Buddleja davidii also has the ability to grow in extremely shallow soil or barely any at all. It's this ability which allows it to grow out of walls, chimney stacks and other built structures. If allowed to mature, its growth can widen existing cracks and weaknesses and cause significant damage to these structures.


Early intervention can limit Buddleja davidii's impact on biodiversity, prevent it spreading, and reduce the structural damage it can cause to built structures, especially listed and historical buildings.


Buddleja davidii growing out of the base of a wall with purple flower head

Features of Buddleja Davidii

  • Long, lance shaped deep green leaves, between 7-13cm in length with a white velvety underside. Forming opposite each other along the length of the stem. 

  • Tall, arching woody stems reaching 5m in height. Quadrangular in shape with pale brown bark, becoming deeply fissured when mature. Younger stems are softer and hairy to the touch.

  • Tiny little lilac/purple flowers produce a long, pyramidal shaped cluster, 15-20cm in length which is loaded with sweet scented nectar (which attracts some species of butterflies).

  • Seeds are contained within a capsule produced in late summer, a single flower cluster can produce over 40,000 seeds. Seeds are spread along watercourses, by wind and birds. Seed bank can remain active for up to 4 years.

Types of Buddleja Davidii Treatment

  • In-situ herbicide treatment: This is the application of herbicide to the foliage. Cut-stump treatment can be used on mature plants. Herbicide treatment is an efficient and effective method for controlling large stands. It is also less labour intensive and intrusive.


  • In-situ manual treatment: Hand pulling, cutting or digging out individual plants which also reduces further contribution to the seedbank. Cut stumps require herbicide treatment to prevent regrowth. Hand pulling is ideal for sensitive areas.


  • Off-site disposal: This option can be used as a last resort when other options are not viable. Buddleja davidii is not on Schedule 9 of the Wildlife and Countryside Act and can be disposed of alongside native shrubs.

Buddleja davidii growing out of a wall on a brownfield site

ERS has extensive experience in identification, management and remediation of Buddleja davidii infested sites. We work with clients to develop a treatment strategy which meets the client's timescales, budget and future development requirements.


When Buddleja davidii is identified on a site, ERS can develop and implement a Management Plan. The plan is essential for both the current owner and any future owners as a record of treatment on the site.


To enquire about a survey or management plan for Buddleja on your land, contact us today to speak to one of our Invasive Weeds experts.

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