Rhododendron ferrugineum

The red rhododendron, or Alpine rose (Rhododendron ferrugineum), belongs to the Ericaceae family and is the type species of the genus Rhododendron; the specific name derives from the rust-coloured scales covering the underside of the leaves.

It is an evergreen ground-covering shrub, generally between 30 cm and 100 cm tall, up to a maximum of 1.5 m, with a highly branched woody stem and fragile, erect or ascending branches. The leaves, clustered at the tips of the branches, are elliptic-lanceolate, leathery, dark green and glossy on the upper surface, and dotted with rust-coloured scales on the underside. It flowers between June and July, continuing into August at higher altitudes: the tubular-campanulate flowers are arranged in terminal racemes of 6–12, with a corolla 1–2 cm long, usually pinkish-red and more rarely white. The fruit is an ovoid capsule 4–11 mm long that splits into five valves when ripe.

It grows on scree slopes, high-altitude grasslands, ledges and slopes with prolonged snow cover, thriving best on siliceous substrates, in the sparse undergrowth of larch (Larix decidua) and Swiss stone pines (Pinus cembra) in the subalpine zone, often in association with bilberry (Vaccinium myrtillus) and on cool, north-facing slopes. It is widespread throughout the entire Alpine arc and the Tuscan-Emilian Apennines, as well as in the Pyrenees and the Jura, generally at altitudes between 1,600 m and 2,800 m, with occasional occurrences at lower elevations.

It shares the common name ‘Alpine rose’ with Rhododendron hirsutum, from which it is distinguished by its growing substrate (acidic rather than calcareous) and by theabsence of hairs on the leaf margins; where the two species coexist, the hybrid Rhododendron × intermedium may form.

The leaves have traditionally been used as a diaphoretic, diuretic, depurative and anti-rheumatic; from the galls produced on the plant by the fungus Exobasidium rhododendri, an ointment known as ‘marmot oil’ was obtained, used to treat rheumatic pains. However, the plant contains toxic glycosides concentrated mainly in the leaves: ingestion can cause gastrointestinal disturbances and, in the most serious cases, cardiovascular disorders, in both humans and grazing livestock. The nectar and honey derived from it do not normally contain the same toxic concentrations found in other species of the genus, such as Rhododendron ponticum.