Buddleja davidii

Identity

Common name: Butterfly bush
Synonyms: Buddleia davidii, Buddleja variabilis
Origin: Asia
Plant type: Shrub
Life cycle: Perennial
Code of conduct: Annex II
Invasive status (ISEIA protocol): Watch list
Main ornemental function: Ornamental shrub

Description

Multi-stemmed shrub up to 5 m tall, semi-deciduous (leaves are shed in the autumn and immediately replaced with a new set of smaller leaves that persist until the following spring). The most common flower color is lilac and purple, but there are many cultivars with varied flower colors ranging from purple, white, yellow and red following the cultivars. Very attractive for insects. It may be found as solitary individuals or in dense thickets.

Spread

This plant may easily escape from gardens. B. davidii has spread first along railways, where seeds were either carried on trains or blown away. One single mature individual can produce millions of seeds. The majority of seeds may be dispersed at 10 meters or greater from the parent. Automobiles have been found to disperse seeds of B. davidii, which can also be spread over long distances through water. The plant can regenerate from stems and root fragments. The species is frequently planted as ornamental.

Habitat

Very popular in gardens, it colonises disturbed and natural areas including floodplains, forest clear-cuts, limestone quarries, chalk rocky areas, railways and roadways. It is actually the most frequent species in wastelands in Brussels. It is a pioneer species toterant to dry soils.

Impact

Species classified B3 in Belgium. B. davidii is considered as invasive in countries like France, the United Kingdom, Switzerland. In Belgium the species is mostly found in urbanised landscapes and disturbed areas considered as less important for nature conservation, which justifies its watch list ranking. However, this plant can form very dense thickets on favourable conditions. It presents a risk for high conservation value habitat like chalk grasslands. The future extension of buddleja populations should be checked. Buddleja is highly attractive for butterflies which feed on it, but not reproduce. For more information, click here

Recommendation

(1) avoid planting this species near rocky habitats (rocky slopes, quarries, chalk grasslands, etc.) or along rivers, especially in the vicinity of protected areas (natural reserves, Natura 2000 sites, etc.) ; (2) cut the flowers at the end of the flowering and before fructification in order to avoid seed dispersal.