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Mahonia aquifolium

Identity

Common name: Oregon grape
Synonyms: Berberis aquifolium, Berberis piperiana, Mahonia piperiana, Odestemon aquifolium
Origin: North America
Plant type: Shrub
Life cycle: Perennial
Code of conduct: Annex II
Invasive status (ISEIA protocol): Black list
Main ornemental function: Ornamental shrub

Description

Shrub up to 0,5 - 2,5 m tall, stoloniferous to stiffly erect. Bark and wood yellowish. Evergreen shiny leaflets with spiny teeth, similar to the native Ilex aquifolium. Yellow flowers. Blue berries.

Spread

High dispersal capacities. Sexual and vegetative reproduction by stem layering. Seeds can colonise new habitats, and clonal growth is predominant in situation of competition with native flora.

Habitat

Mahonia aquifolium is increasingly found in semi-natural habitats like dunes, rock outcrops, grassland and woodlands (pine forests). Tolerant to shade and normally grows in the forest understory. It prefers calcarous soils and can grow in dry and moist conditions.

Impact

Species classified A2 in Belgium. Aggressive invader of some forest in central and eastern Germany, where M. aquifolium is considered as one of the most succesfull alien shrub. Populations with high seedling densities. The strong vegetative development of Oregon grape leads to the formation of large and dense populations that are likely to overgrow and outcompete native species. Potentially invasive in Austria and Switzerland. In Belgium, the species is present in chalk grasslands and in dunes. For more information about this species, click here

Recommendation

(1) Avoid planting this species near coastal dunes and rocky habitats, especially in the vicinity of protected areas (natural reserves, Natura 2000 sites, etc.) ; (2) cut the flowers at the end of flowering and before fructification in order to avoid seed dispersal.

Possible native alternative

Main ornemental function

Ornamental shrub

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