Rhododendrons

 

 

The word rhododendron is derived from the Greek rodo (‘rose’) and dendron (‘tree’), thus meaning ‘rose tree’. It seems that to the ancient Greeks, the flowers clusters of certain rhododendron species resembled roses. However, these trees and shrubs are not at all related to roses, but belong to the heath family (Ericaceae). From a distance, though, the flower clusters of some species do resemble roses.

 

 

One species, whose flower clusters resemble roses, at least from a distance, is Rhododendron barbatum, here photographed near Tharepati, Langtang National Park, central Nepal. (Photo copyright © by Kaj Halberg)

 

 

 

The genus Rhododendron is huge, comprising c. 1,025 species worldwide, found mainly in temperate and subtropical areas of Eurasia, North America, Tropical Asia, and New Guinea, with the largest concentrations encountered in south-western China, the Himalaya, the Greater Sunda Islands, and New Guinea. China is the absolute stronghold of the genus, with no less than c. 571 species, of which 409 are endemic.

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.

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.

 

 

An unidentified rhododendron species, Wumeng Shan Mountains, Guizhou Province, China. (Photo copyright © by Kaj Halberg)

 

 

This woman in the Wumeng Shan Mountains has just picked fresh rhododendron flowers and leaves, held by her small son. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendrons vary greatly in size, from dwarf shrubs like R. pumilum, R. nivale, and R. lapponicum, which are usually less than 20 cm high, to Himalayan species like R. arboreum and R. grande, which can grow to 15 m tall.

 

 

Rhododendron arboreum, a widespread Asian species, can grow to 15 m tall. (Photo copyright © by Kaj Halberg)

 

 

Rhododendron setosum is a very common dwarf shrub in the Himalaya. It rarely grows taller than 50 cm. It is described in detail below.

 

 

 

The fruit is a capsule, containing between four and twenty chambers. In the pictures below, fruits from the previous year are still sitting on the plant.

 

 

Fruit cluster of Rhododendron arboreum, Helambu, Nepal. (Photo copyright © by Kaj Halberg)

 

 

Fruit cluster of Pacific rhododendron (Rhododendron macrophyllum), Redwood National Park, California. (Photo copyright © by Kaj Halberg)

 

 

 

Many rhododendron species are very tough, growing under severe climatic conditions. Four examples are shown below.

 

 

Rhododendron arboreum forest, Langtang National Park, central Nepal. (Photo copyright © by Kaj Halberg)

 

 

Rhododendron campanulatum, likewise in Langtang National Park. (Photo copyright © by Kaj Halberg)

 

 

Early in the morning, the flowers of this Rhododendron fulgens, growing in the Barun Valley, eastern Nepal, are covered in rime. This species is found at high altitudes in the Himalaya, from eastern Nepal eastwards to south-eastern Tibet. (Photo copyright © by Kaj Halberg)

 

 

Rime-covered flowers and leaves of an unidentified species, Wumeng Shan Mountains, Guizhou Province, China. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron anthopogon
Dense thickets of this dwarf shrub, in Nepali called sun pathi, cover large areas in the Himalaya, at altitudes between 3,000 and 5,100 m. Dried flowers of this plant are utilized as tea, and its branches are burned as incense in temples and on house altars.

 

 

Rhododendron anthopogon, Gokyo Valley, Khumbu, eastern Nepal. (Photo copyright © by Kaj Halberg)

 

 

This man from the Gosainkund area of central Nepal shows a tray, full of dried sun pathi flowers. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron arboreum
This species, which is among the highest members of the genus, grows to 15 m tall. It is very common in the Himalaya, and in March-April, when it is flowering, it adds a reddish or pinkish tinge to the forest in numerous places, stemming from millions of flowers. The intensity of the red flower colour decreases with altitude, and near the upper limit of its distribution, around 3,800 m, you sometimes encounter trees with white flowers. This species is the national plant of Nepal, called lali guras (’red rhododendron’).

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 the Annapurna area, central Nepal, where these pictures were taken, Rhododendron arboreum, when flowering, adds a reddish or pinkish tinge to the large tracts of forest. (Photos copyright © by Kaj Halberg)

 

 

Nepal 2008
Various flower colours of Rhododendron arboreum. (Photos copyright © by Kaj Halberg)

 

 

This inflorescence of Rhododendron arboreum, seen in Helambu, Nepal, is still unfolded. (Photo copyright © by Kaj Halberg)

 

 

In spring, the flowers of Rhododendron arboreum produce a profusion of pollen. For this reason, they are much visited by various bird species, in this picture a striated laughing-thrush (Grammatoptila striata). – Annapurna, central Nepal. (Photo copyright © by Kaj Halberg)

 

 

Nepal 1994-95
Little children in eastern Nepal, one with an armload of Rhododendron arboreum flowers. Cleanliness seems to be of less importance in this area! (Photo copyright © by Kaj Halberg)

 

 

This picture shows Nilgiri rhododendron (R. arboreum ssp. nilagiricum), photographed in the Nilgiri Mountains, Tamil Nadu. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron barbatum
From a distance, this species is quite similar to R. arboreum, but a closer look reveals distinctive glandular bristles on its twigs and leaf-stalk, and its bark peels off in thin, cinnamon-coloured flakes. It is very common in the Himalaya, found from Uttarakhand eastwards to Bhutan.

 

 

Rhododendron barbatum often forms pure stands at altitudes between 2,400 and 3,600 m, as in this picture from Kutumsang, Langtang National Park, central Nepal. (Photo copyright © by Kaj Halberg)

 

 

This picture from Ghorepani, Annapurna, central Nepal, shows the distinctive bristles on a twig of Rhododendron barbatum. (Photo copyright © by Kaj Halberg)

 

 

The bark of Rhododendron barbatum peels off in thin, cinnamon-coloured flakes. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron brookeanum
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.

The pink-flowered R. brookeanum, now often regarded as a subspecies of the widespread R. javanicum, is quite common in the forest on Gunung Kinabalu, at about 2,000 m altitude.

 

 

(Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron calendulaceum Flame azalea
This plant is distributed in eastern United States, from Pennsylvania and Ohio southwards to Georgia and Alabama, with a stronghold in the Appalachian Mountains. Due to its gorgeous flowers, it is widely cultivated elsewhere.

 

 

These flame azalea in Maudsley State Park, Massachusetts, are escapes from earlier cultivation. (Photos copyright © by Kaj Halberg)

 

 

 

Rhododendron campanulatum Bell rhododendron
The specific name of this species, from the Latin campanula (‘little bell’), refers to its strongly bell-shaped flowers. This attractive shrub is very common in the Himalaya, forming dense thickets at altitudes between 2,800 and 4,000 m.

 

 

Nepal 2013
Bell rhododendron, Ghunsa Valley, eastern Nepal. (Photos copyright © by Kaj Halberg)

 

 

One characteristic of bell rhododendron is the rusty-coloured layer of hairs on the underside of its leaves. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron campylocarpum
A very common plant, distributed from eastern Nepal eastwards to south-western China, at altitudes between 3,000 and 4,000 m. In places, it brightens large tracts of forest with its beautiful pale-yellow inflorescences.

 

 

Rhododendron campylocarpum is very common in the Khumbu area, eastern Nepal, where these pictures were taken. (Photos copyright © by Kaj Halberg)

 

 

Rhododendron campylocarpum, photographed near the Buddhist monastery Tengboche, Khumbu. The peaks of Nuptse (7879 m, at left), Sagarmatha (Everest) (8850 m, behind Nuptse), and Lhotse (8511 m, centre) are seen in the background. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron catawbiense Catawba rhododendron
This species is very common at higher altitudes in the southern part of the Appalachian Mountains, eastern United States.

 

 

Catawba rhododendron with raindrops, Pisgah National Forest, North Carolina. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron ciliatum 
This small shrub, whose white or slightly pinkish flowers have five notched, overlapping lobes, has a very limited distribution, from eastern Nepal eastwards to Bhutan. It often grows on rocks, at altitudes between 2,700 and 3,900 m.

 

 

Rhododendron ciliatum, Barun Valley, eastern Nepal. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron cinnabarinum
This plant grows at altitudes between 3,200 and 4,000 m, from eastern Nepal eastwards to south-western China. It is distinguished by the long, tubular, waxy, pendent flowers, which are usually dark red. Occasionally, though, paler flowers occur.

 

 

Nepal 2013
Rhododendron cinnabarinum is common in the Ghunsa Valley, eastern Nepal, where these pictures were taken. The lower picture shows a plant with purplish-pink flowers. (Photos copyright © by Kaj Halberg)

 

 

 

Rhododendron columbianum Western Labrador tea
Previously, this plant, also known as trapper’s tea, was named R. neoglandulosum, and prior to that Ledum columbianum. It is distributed in western North America, from British Columbia and Alberta southwards to California, Utah, and Colorado. It is partial to wet places, from sea level up to an altitude of about 3,500 m. As its popular names imply, tea was formerly brewed on the leaves.

 

 

Western Labrador tea, encountered in Kruse State Forest, California. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron cumberlandense Cumberland azalea
This plant is quite similar to flame azalea (above), but flowers and leaves are smaller, and when mature, the leaves have a waxy bloom on the underside. Its style and filaments are brick-red, whereas they are yellow, orange, or pink in flame azalea. Cumberland azalea has a limited distribution in eastern America, found from the Cumberland Plateau in Kentucky southwards to Georgia, Alabama, and North Carolina.

 

 

Cumberland azalea, Cades Cove, Great Smoky Mountains National Park, Tennessee. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron dalhousiae
Joseph Dalton Hooker (1817-1911) was a British botanist, who, during the period 1848-1850, described no less than 22 new rhododendron species from Sikkim and other parts of the eastern Himalaya, including this gorgeous species, which was named in honour of Lady Dalhousie, wife of George Ramsay, the 9th Earl of Dalhousie, who was governor-general in India in the first half of the 1800s. Lady Dalhousie was an avid collector of plants.

In April-May, this epiphytic species displays a profusion of lemon-coloured flowers, which later turn yellowish-white.

 

 

Rhododendron dalhousiae, Tashigaon, Arun Valley, eastern Nepal. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron delavayi
This magnificent plant is distributed in south-western China, south-eastern Tibet, Bhutan, Arunachal Pradesh in north-eastern India, and in mountains of northern Myanmar, Thailand, and Vietnam.

 

 

Rhododendron delavayi, Wumeng Shan Mountains, Guizhou Province, China. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron ericoides
This shrub is restricted to higher altitudes, between 2,700 and 4,000 m, on Gunung Kinabalu, Borneo. It is easily identified by the red, funnel-shaped flowers and tiny leaves, which are reminiscent of those of crowberry (Empetrum nigrum).

 

 

(Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron ferrugineum Rusty-leaved alpenrose
This small shrub is the commonest European species, distributed in the Pyrenees, the Alps, the Jura Mountains, and the northern part of the Apennines. It often covers large areas of mountain slopes at elevations between 1,600 and 2,200 m, especially on acid soils. Its name stems from a rusty-coloured layer of hairs, covering the underside of the leaves, which has also given rise to the specific name, from the Latin ferrum (‘iron’).

 

 

Rusty-leaved alpenrose often covers large areas of mountain slopes, as here in the Grossglockner area, Austria. (Photo copyright © by Kaj Halberg)

 

 

Rusty-leaved alpenrose, Grossglockner area. Striped daphne (Daphne striata) is seen in the background. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron hirsutum Hairy alpenrose
Another common European species, which grows on carbonate-rich soils in the Alps, from Switzerland eastwards, and in the Carpathians, where it may be introduced. It is easily identified by its ciliate leaves, and its flowers are also more pinkish than those of rusty-leaved alpenrose. Where the distribution of these species occasionally overlap, hybrids between them are frequent.

 

 

Hairy alpenrose, Berner Oberland, Switzerland. A common spotted orchid (Dactylorhiza maculata ssp. fuchsii) is also seen in the upper picture. (Photos copyright © by Kaj Halberg)

 

 

 

Rhododendron hodgsonii
This large shrub, which grows to 7 m tall, is easily identified by its dense inflorescences and large leaves. The flower colour varies from whitish to deep pink. It has a rather limited distribution, from eastern Nepal eastwards to south-eastern Tibet.

 

 

My guide Saila Tamang, standing in a dense growth of Rhododendron hodgsonii, Barun Valley, eastern Nepal. (Photo copyright © by Kaj Halberg)

 

 

Rhododendron hodgsonii, Barun Valley (top), and Ghunsa Valley, both in eastern Nepal. (Photos copyright © by Kaj Halberg)

 

 

 

Rhododendron lapponicum Lapland rhododendron
This dwarf shrub, also known as Lapland rosebay, is distributed in subarctic regions of the Northern Hemisphere. It comes in two varieties, lapponicum of Eurasia, and parvifolium in eastern Siberia and North America.

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. 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)

 

 

Chukotka 2011
Lapland rhododendron, var. parvifolium, photographed on the Chukotka Peninsula, eastern Siberia. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron lepidotum
Flowers of this dwarf shrub come in three colour forms, red, white, and (rarely) yellowish. This is one of the most widespread Himalayan rhododendron species, distributed from northern Pakistan eastwards to south-western China. It also has a wide altitudinal range, found between 2,400 and 4,500 m.

 

 

The commonest flower colour of Rhododendron lepidotum is red, here encountered in Langtang National Park, central Nepal. Note the ant in the flower. (Photo copyright © by Kaj Halberg)

 

 

White-flowered form, Ghunsa Valley, eastern Nepal. (Photo copyright © by Kaj Halberg)

 

 

The rare yellowish form, encountered in the Gokyo Valley, Khumbu, eastern Nepal. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron luteum Yellow azalea
Yellow azalea is distributed from Poland southwards through Austria to the Balkans, and thence eastwards to the Caucasus. Its sweet-smelling flowers attract bees, but the honey produced from them is actually toxic, and reports of people being poisoned by consuming this honey date as far back as Classical Greece.

 

 

Yellow azalea, photographed on the Turkish Black Sea coast, near the town of Tirebolu. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron macrophyllum Pacific rhododendron
As its name implies, this species is distributed along the North American Pacific Coast, from Monterey Bay in California northwards to British Columbia. It is mainly coastal, but is also found rather far inland in the Cascade Mountains of Oregon, Washington, and British Columbia.

 

 

Pacific rhododendron, photographed near Trinidad, California. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron morii
Formerly, this plant, which is distributed in central and eastern Taiwan, was regarded as a subspecies of R. pseudochrysanthum (below). Its flower colour comes in all shades between snow-white and pale pink.

 

 

Taiwan 2008
The white-flowered form of Rhododendron morii, Hohuan Shan. (Photos copyright © by Kaj Halberg)

 

 

Taiwan 2014b
Pinkish form of Rhododendron morii, photographed on a foggy day in montane forest, Taipingshan National Forest, Taiwan. (Photos copyright © by Kaj Halberg)

 

 

 

Rhododendron nivale 
The alpine zone above the tree limit in the Himalaya is home to several species of dwarf rhododendron, including R. nivale, which is distributed from western Nepal eastwards to south-western China, at altitudes between 4,500 and 5,500 m. It is quite similar to R. setosum (below), but the leaf margin of that species usually has bristles, and its funnel-shaped corolla is reddish-violet, whereas R. nivale has darker violet, smaller flowers, and no bristles on the leaves. Generally, R. nivale grows in drier areas than R. setosum.

 

 

Everest 2010
Rhododendron nivale, photographed in the Khumbu region, eastern Nepal. (Photos copyright © by Kaj Halberg)

 

 

 

Rhododendron nudiflorum, see R. periclymenoides.

 

 

 

Rhododendron occidentale Western azalea
This deciduous species grows in coastal ranges of western North America, from Oregon southwards to the Mexican border. It is not known to occur east of the Cascade and Sierra Nevada Mountains.

 

 

USA-Canada 1992
Western azalea, Cave Junction, Oregon. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron oldhamii
Flowers of the majority of the c. 30 Taiwanese rhododendron species display white, pinkish, or violet colours, but those of Rhododendron oldhamii are a warm red. This species is found almost down to sea level, whereas most of the other Taiwanese species grow at high altitudes in the central part of the island.

 

 

Rhododendron oldhamii, photographed near Nanren Lake, Kenting National Park, southern Taiwan. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron periclymenoides Pinxter flower
This species, also called R. nudiflorum, is distributed in eastern United States, from Massachusetts southwards to North Carolina, and westwards to western Kentucky and eastern Tennessee. The common name is derived from the Dutch Pentecost, a name used for the seventh Sunday after Easter. Pinxter flower typically blooms around this time.

 

 

Pinxter flower, photographed at Pohatcong Creek, New Jersey. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron ponticum Pontic rhododendron
During his travel in the Middle East 1700-1702, French physician and botanist Joseph Pitton de Tournefort (1656-1708) encountered a species of rhododendron, growing on the Black Sea coast in the area of Pontus, in present-day north-eastern Turkey and Georgia. For this reason, Swedish naturalist Carolus Linnaeus (1707-1778), also called Carl von Linné, named it Rhododendron ponticum. The nominate subspecies is native to the Caucasus, Turkey, Lebanon, and Bulgaria, whereas small populations of subspecies baeticum are distributed in south-western Spain and Portugal.

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 and Ireland, it is a widespread menace, which has colonized numerous hillsides, moorlands, and shady woodlands, often replacing local plant species.

 

 

Rhododendron ponticum, photographed near the town of Espiye, on the Turkish Black Sea coast, where it is a native. (Photos copyright © by Kaj Halberg)

 

 

 

Rhododendron pseudochrysanthum
This gorgeous shrub is found at very high altitudes in the mountains of Taiwan, between 3,100 and 3,900 m. Its flowers are white or pink.

 

 

Taiwan 2016
Taiwan 2016
Rhododendron pseudochrysanthum is common in the Hohuan Shan Mountains, where these pictures were taken. (Photos copyright © by Kaj Halberg)

 

 

 

Rhododendron pumilum
This plant rarely grows taller than 10 cm, reflected in its specific name, which is derived from the Latin pumilio (‘dwarf’). Its habitat is open slopes and rocks. It is distributed from eastern Nepal eastwards to south-western China, growing at altitudes from 3,600 to 4,300 m.

 

 

Rhododendron pumilum, Barun Valley, eastern Nepal. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron retivenium
Two rhododendron species are quite common in the forest at about 2,000 m altitude on Gunung Kinabalu, the highest mountain on Borneo, the yellow-flowered R. retivenium and the pink-flowered R. brookeanum (above).

 

 

Rhododendron retivenium, Gunung Kinabalu. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron rubropilosum Red-hairy azalea
This species may be identified by the reddish-brown, glandular hairs on twigs and leaves. It is restricted to central Taiwan, at altitudes between 1,800 and 3,300 m, often forming large thickets at higher altitudes.

 

 

Rhododendron rubropilosum, Hohuan Shan. (Photos copyright © by Kaj Halberg)

 

 

 

Rhododendron setosum
The funnel-shaped flowers of this dwarf shrub are usually reddish-violet, but a form with pink flowers is occasionally seen. It is quite similar to R. nivale (above), but its leaf margin usually has bristles, whereas R. nivale has no bristles on its leaves, and darker violet, smaller flowers. R. setosum is found on alpine slopes at slightly lower altitudes than R. nivale, between 3,600 and 4,800 m. It is distributed from central Nepal eastwards to south-western China.

 

 

Rhododendron setosum, photographed in the Khumbu region, eastern Nepal. The lower picture shows the pink-flowered form, next to flowers of a normal colour. (Photos copyright © by Kaj Halberg)

 

 

 

Rhododendron simsii
This shrub, growing to 2 m tall, is distributed in southern China and northern Indochina. The flower colour ranges from white to dark red. The specific name commemorates English botanist and physician John Sims (1749-1831) who was the first editor of Curtis’s Botanical Magazine.

 

 

Rhododendron simsii, Guizhou Province, China. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron thomsonii
This shrub, growing to 5 m tall, is easily identified by its broadly bell-shaped, waxy, fleshy flowers, and the rather small, pinkish-red calyx. It grows in open areas, preferably near streams, at altitudes from 3,000 to 3,800 m. It is distributed from eastern Nepal to south-eastern Tibet.

 

 

Nepal 2013
Nepal 2013
These pictures are from the Ghunsa Valley, eastern Nepal, where Rhododendron thomsonii is quite common. (Photos copyright © by Kaj Halberg)

 

 

 

Rhododendron tomentosum Marsh Labrador tea
This plant, previously called Ledum palustre, is very common and widespread in wetter areas of the boreal zone in the Northern Hemisphere. It comes in two subspecies, tomentosum, found from Scandinavia eastwards to the Taimyr Peninsula, and decumbens, which is distributed from the Taimyr Peninsula eastwards across Siberia to Alaska, Canada, and Greenland. Subspecies subarcticum is now regarded as synonymous with decumbens.

 

 

Chukotka 2011
Marsh Labrador tea, ssp. decumbens, photographed on the Chukotka Peninsula, eastern Siberia. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron triflorum
The flowers of this small shrub, growing to 3 m tall, are a very pale yellow with a greenish tinge, arranged in clusters of three, as indicated by its specific name. The bark peels off in thin, cinnamon-coloured flakes. This species is found in shrubberies from eastern Nepal eastwards to south-eastern Tibet, at altitudes from 2,400 to 3,300 m.

 

 

Rhododendron triflorum, Ghunsa Valley, eastern Nepal. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron vaseyi Pinkshell azalea
This plant has an extremely limited distribution, found only in the Appalachian Mountains in North Carolina.

 

 

USA 2012
Following a heavy shower, these pinkshell azalea flowers in Pisgah National Forest are covered in rain drops. (Photo copyright © by Kaj Halberg)

 

 

 

Rhododendron wallichii 
Formerly, this Himalayan species was regarded as a variety of R. campanulatum (above), but generally its flowers are paler, and the underside of the leaves is not hairy. The specific name was given in honour of Danish physician and botanist Nathaniel Wallich (1786-1854), who studied the Indian and Himalayan flora in the early 1800s.

 

 

These pictures are from the Khumbu area, eastern Nepal, where Rhododendron wallichii is very common. (Photos copyright © by Kaj Halberg)

 

 

 

Rhododendron wightii
This plant, which grows to 4 m tall, forms shrubberies many places in the eastern Himalaya, from eastern Nepal eastwards to south-eastern Tibet, at altitudes between 3,300 and 4,300 m. Its leaves are large, to 20 cm long, with felt-like, rusty hairs beneath, and the bell-shaped flowers are white or very pale yellow, with crimson blotches within.

 

 

Rhododendron wightii, Barun Valley, eastern Nepal. In the upper picture, it is photographed in front of a dark rock, named Neh. (Photos copyright © by Kaj Halberg)

 

 

 

 

Rhodothamnus
Members of this genus, called dwarf alpenroses, have been placed in a separate genus, as they differ in certain characters from true rhododendron species. The genus contains only two species, the Eurasian dwarf alpenrose (R. chamaecistus), which is distributed in the central and eastern Alps, and R. sessilifolius, which is restricted to a small montane area, Tiryal Dağı, in the Artvin Province, north-eastern Turkey.

 

 

Eurasian dwarf alpenrose, Passo di Valparola, Dolomites, Italy. (Photos copyright © by Kaj Halberg)

 

 

(Uploaded August 2017)

 

(Latest update August 2020)