Rhododendron ferrugineum, the alpenrose, snow-rose, or rusty-leaved alpenrose is an evergreen shrub that grows just above the tree line in the Alps, Pyrenees, Jura and northern Apennines, on acid soils. It is the type species for the genus Rhododendron. It may grow up to 14 m (46 ft) tall and produces clusters of pinkish-red, bell-shaped flowers throughout the summer. The undersides of the leaves are covered in rust-brown spots, which give the species the second part of its binomial name (ferrugineum, Latin for 'rust-coloured, ferruginous'). This is in contrast to Rhododendron hirsutum, which has no such brown colouring, has hairy edges to the leaves and grows over limestone. Where the two species co-occur (usually on soils of intermediate pH), the hybrid Rhododendron × intermedium may occur; as its name suggests, it is intermediate in form between the two parental species.
Rhododendron ferrugineum is moderately toxic, containing arbutin, arecoline and rhodoxanthin, and can cause vomiting, and difficulties of the digestive, nervous, respiratory and circulatory systems.
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