Rhododendrons

 

 

 

 

 

 

 

The Himalaya is home to c. 100 species, the vast majority growing in the eastern part of the mountain chain. A tiny country like Bhutan, for instance, harbours more than 60 species. The further west you travel in the Himalaya, the fewer species you encounter. Eastern Nepal is home to c. 30 species, western Nepal to seven, and Pakistan to only four. The genus occurs in almost all vegetation zones, from subtropical to alpine, the major part found between 2,000 and 4,000 m altitude.

In tropical regions, the genus is mainly restricted to mountains, but a few species are found in areas with a genuine tropical climate, including one in Queensland, Australia.

Montane areas of Borneo hold c. 55 species of rhododendron, about half of which are restricted to the highest mountains on the island, around Gunung Kinabalu (4094 m). The interesting flora and fauna in this area is described on the page Travel episodes – Borneo 1985: A hike up Gunung Kinabalu.

In North America, 27 rhododendron species are found, with the highest concentration in the eastern part of the continent, mainly in the Appalachian Mountains. Europe, including the Caucasus, is home to 12 species, and a few species are distributed in Arctic areas.

The name Rhododendron is used for evergreen as well as deciduous species, the latter often called azalea. European species are usually called by their German name, Alpenrose.

The inflorescence of most species is an umbel-like cluster, the corolla being funnel- or bell-shaped, with five lobes. The commonest flower colours are various shades of red, pink, or lilac. White and yellow flowers are also frequent, whereas greenish is only seen in a few species.

Previously, species of Labrador tea, or muskeg tea, were placed in a separate genus, Ledum, but genetic analyses have revealed that they are in fact rhododendrons. The names Labrador tea and muskeg tea refer to the usage of the leaves of these plants for tea, and they were also formerly added to beer, similar to bog myrtle (Myrica gale). Due to their powerful fragrance, they were also utilized to deter moths from clothes.

A selection of Himalayan rhododendron species are described in depth on the page Plants: Himalayan flora 1.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In its widest sense, this species has an extensive distribution in Asia, from Pakistan eastwards to montane areas of northern Thailand and Vietnam, with isolated subspecies in mountains of South India, the Nilgiri rhododendron (R. arboreum ssp. nilagiricum), and in Sri Lanka, R. arboreum ssp. zeylanicum. These subspecies are regarded as separate species by some authorities.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In April-May, this epiphytic species displays a profusion of lemon-coloured flowers, which later turn yellowish-white. It occurs from central Nepal eastwards to the eastern Himalaya, found at elevations between 2,000 and 2,500 m.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Martin Henrichsen Vahl (1749-1804) was a Danish-Norwegian naturalist, who studied botany at the University of Copenhagen, and also at Uppsala University under the famous Carl Linnaeus. Vahl was a lecturer at the University of Copenhagen Botanical Garden 1779-1782, and was the editor of several botanical works, including Flora Danica, Vol. XVI-XXI, Symbolæ Botanicæ, Vol. I-III, Eclogæ Americanæ, Vol. I-IV, and Enumeratio Plantarum, Vol. I-II.

In 1787, Vahl travelled to Norway in search of plants to be illustrated in Flora Danica. (Norway was then a Danish territory.) From Copenhagen, he went by ship to Christiania (Oslo), then north through the Gudbrand Valley and further on to the town of Lom, situated at the foot of the highest peaks of Norway, in Jotunheimen and Dovre. In 1792, Vahl wrote enthusiastically about a botanical trip near the town: “One of the rarest Norwegian plants, Azalea lapponica, was ample reward for struggling towards the peak of a high mountain, through snow and morass. The pleasure of having seen this plant alive was further increased by the fact that it might easily have escaped my attention, as only two bushes were growing here.” (Source: H. Knudsen 2014. Fortællingen om Flora Danica. Lindhardt & Ringhof, in Danish)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In 1763, Pontic rhododendron was introduced to Britain as an ornamental, and it was also planted as cover for game birds. It quickly became naturalized, spreading by suckers on the tips of the branches. Today, in England, Wales, and Ireland, it is a widespread menace, which has colonized numerous hillsides, moorlands, and shady woodlands, often replacing local plant species.