As with other areas, Glenveagh has to contend with the highly invasive Rhododendron ponticum. This non-native plant was introduced to Ireland in the early 19th century primarily for ornamental purposes.
Rhododendron thrives on well drained, acid soils in mild, damp climates, and has naturalised in such situations across Britain and Ireland. It reproduces mainly by the production of large amounts of seed. A single bush in Killarney standing 2 metres tall by 10 metres circumference, produced more than 1 million seeds. Rhododendron has relatively few insects associated with it in Ireland and Britain, and is poisonous to grazers such as sheep, deer and cattle.
If left unmanaged, rhododendron stands will out-compete native flora in woodland and peatland habitats, causing severe degradation in their quality. This in turn can have an adverse effect on the fauna that depend on those habitats and to the wider surrounding ecosystem.