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© P. Brusselen
© S. Vanderhoeven
© S. Vanderhoeven
© M. Halford
© M. Halford
© M. Halford
© M. Halford

Invaded site

© M. Halford
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Robinia pseudoacacia

Identity

Common name: Black locust, False acacia
Synonyms: Pseudoacacia odorata, Pseudoacacia comunis, Pseudoacacia pseudoacacia, Robinia acacia
Origin: North america
Plant type: Tree
Life cycle: Perennial
Code of conduct: Annex II
Invasive status (ISEIA protocol): Watch list
Main ornemental function: Ornamental shrub • Ornamental tree

Description

Deciduous tree up to 10 - 25 m tall. Older trees have a deeply dark brown bark with flattopped ridges. Main stem is sinous. Leaves glabrous, alternate, compound with 7 to 21 leaflets. Leaflets elliptic to ovate. Very fragrant white flowers.

Spread

Literature describes the black locust as a species of high dispersal capacities, producing numerous wind-dispersed seeds (viable in the soil during at least 10 years) and also reproducing vegetatively by root suckering and resprouting. Growing rate is high (up to 2 m high in one year). In Belgium, dispersal capacities are moderate. Sexual reproduction is uncertain. Although this tree produces abundant seeds, germination rate is often low. Nevertheless, field observations of seedlings, coupled with genetic studies indicate that R. pseudoacacia may reproduce by seeds in nature.

Habitat

Pioneer species. R. pseudoacacia is an early successional plant, preferring full sun, well drained soils, and little competition. It is commonly found in disturbed areas such as fallow lands, roadsides, railways. It is reported to invade dry grasslands and forests dominated by light-demanding tree species (oak, pine, etc.), but also wetlands like alluvial forests, riverbanks, tall herbs community. Resistant to drough and pollution.

Impact

Species classified B3 in Belgium. Mentionned as highly invasive in Northern Italy, Switzerland, France, Germany. It colonises habitats of high conservation value like chalk or sandy grasslands, characterized by a diversified flora and rare plant species. Once introduced, the black locust expands readily by root suckering and stump sprouting and forms dense clones creating shaded islands from which most native plants are outcompeted. The large, fragrant blossoms of R. pseudoacacia are sometimes reported to compete with native plants for pollinating bees. It also modifies soil properties and favours the development of a nitrogen-demanding vegetation, modifying the botanical composition. Losses of biodiversity in invaded sites are reported in France and Germany. In Belgium, invasion by R. pseudoacacia is less important, but the species has been observed in chalk grasslands, sandy grasslands, quarries or woodlands in urba areas. For more information about this species, click here

Recommendation

(1) avoid planting this species near dry or rocky habitats, chalk grasslands, sandy grasslands, especially near natural reserves or protected areas ; (2) put a rhizome barrier when planting in order to limit lateral expansion.

Possible native alternatives

Main ornemental function

Ornamental shrub
Ornamental tree

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