Alpenrose
Rhododendron ferrugineum · Ericaceae
📷 Uoaei1 · CC BY-SA 4.0
The gardener's calendar
Ideal time to plant alpenrose: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.
ID card
- Common name
- Alpine Rhododendron
- Family
- Ericaceae
- Foliage
- Evergreen
- Flowering
- June to August, bright pink to red flowers
- Adult size
- 0.5 to 1.5 m in height
- Hardiness
- Very hardy, down to -20 °C
- Origin
- Alps and Pyrenees
- Soil type
- Acidic, well-drained, rich in organic matter
Expert tips
The key tip
Arrose régulièrement en été avec de l'eau douce ou de pluie, jamais calcaire : le calcaire tue le rhododendron ferrugineum. L'idéal est un sol acide, bien drainant, enrichi de terre de bruyère à la plantation. Paille-le pour maintenir l'humidité et la fraîcheur racinaire, surtout en montagne où le soleil tape fort.
The common mistake
Utiliser de l'eau du robinet calcaire ou planter dans un sol neutre/alcalin. La plupart des jardiniers ignorent que cette plante est extrêmement sensible au calcaire : elle jaunit progressivement (chlorose ferrique), arrête de fleurir et meurt lentement.
The pro's trick
Fais un test simple : prélève l'eau qui stagne au pied après arrosage et goutte-la sur du papier pH ou un carrelage blanc. Si elle laisse des traces blanches, c'est du calcaire. Dans ce cas, arrose à l'eau de pluie collectée ou ajoute un chélate de fer à l'eau calcaire.
Seasonal watch
En été, surveille les araignées rouges par temps sec et chaud : le feuillage devient grisâtre. Brumise le feuillage en fin d'après-midi en juillet-août. En automne-hiver en montagne, protège les jeunes plants du vent desséchant et du gel violent avec un paillis épais.
Care
Watering
Water regularly during the growing and flowering periods to keep the soil moist but not waterlogged. Reduce watering in winter. Prefer rainwater or demineralised water, as the plant appreciates acidic soil.
Light exposure
Place the rhododendron in partial shade or dappled light. Intense direct sunlight can scorch the foliage and reduce flowering. In mountain regions, it tolerates more sun thanks to ambient humidity.
Soil
Prepare an acidic substrate with ericaceous compost or specialized potting mix for acid-loving plants. Enrich with well-decomposed compost and ensure excellent drainage to prevent root suffocation.
Pruning and maintenance
Remove spent flowers after flowering to encourage branching. Light pruning after flowering is sufficient to maintain a compact shape. Avoid severe pruning which may compromise the following year's flowering.
Fertilizer
Apply a specific fertilizer for acid-loving plants in spring, during the active growth phase. Moderate feeding is sufficient; excess fertilizer can reduce hardiness and flowering.
Diseases and pests
Watch for powdery mildew in humid, poorly ventilated conditions. Scale insects and spider mites can appear in dry indoor environments. Avoid stagnant excessive moisture which promotes root rot.
Did you know?
Rhododendron ferrugineum is an endemic species of alpine and Pyrenean mountains, adapted to extreme high-altitude conditions. Its name 'ferrugineum' means 'rust-coloured', referring to the underside of its leaves covered with tiny reddish scales that provide protection against evaporation in high mountains. This remarkable strategy makes it a precious plant for gardeners in mountain or northern climates.
Where to buy it
Best planted in autumn so the roots settle in before summer, or in early spring once the frost has passed. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, October, November.
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Tips generated and checked by Viridia — adapt them to your local climate.