Most rhododendron species are shrubs or small trees, which bloom between March and July, with a peak in April-May. A majority of the species display flowers of various shades of red, yellow, or white, whereas violet and greenish are rarely seen.
In the Himalaya, rhododendron species occur in almost all vegetation zones, from subtropical to alpine, the major part growing between 2,000 and 4,000 metres altitude. The largest species is Rhododendron arboreum, which can grow to 15 metres tall. It is the national plant of Nepal, called lali guras. At the opposite end of the spectrum are various dwarf shrubs, such as R. nivale, R. lepidotum, R. anthopogon, and R. pumilum, the latter being only 10-15 centimetres high. Other species are epiphytes, such as the large-flowered R. dalhousiae and R. lindleyi.
The Barun Valley constitutes a part of Makalu-Barun National Park, which was established in 1992, covering an area of c. 1,500 square kilometres. To the west, the park borders Sagarmatha National Park, covering 1148 square kilometres, to the north the huge Qomolangma Nature Preserve in Tibet, covering c. 35,000 square kilometres, and to the south a buffer zone, covering 830 square kilometres. Thus, the valley is situated in the heart of an enormous protected area.
To hike in Makalu-Barun National Park, you need a permit from the National Park Office in Kathmandu, which can be obtained by paying a fee. Tents and cooking equipment must be brought along, as there are no facilities above the village of Tashigaon. Burning wood in the park is strictly prohibited. With an annual precipitation of c. 3,500 millimetres, the area is one of the wettest in Nepal. Even in May – well before the monsoon period – a hike in this park can become a rather wet experience, with many leeches.
The area is home to a tremendous number of plants – more than 3,000 species have been found within the park boundaries. In May, you may encounter no less than 25 blooming rhododendron species, and the park is also home to e.g. 47 orchid species, 48 primrose species, 19 bamboo species, and 15 species of the beech family, belonging to the genera Quercus, Cyclobalanopsis, Castanopsis, and Lithocarpus. More than 400 bird species have been observed, and the park is also a refuge for several threatened mammals, such as clouded leopard (Neofelis nebulosa), red panda (Ailurus fulgens), and Himalayan musk deer (Moschus chrysogaster).
The following morning, we commence our hike, heading north along a ridge on the eastern side of the valley. Up to an altitude of c. 1,800 metres, most of the forest has been cleared for farmland. Along the trail, we often notice tiger’s milk-spruce (Falconeria insignis), formerly called Sapium insigne, a tree of the spurge family, which grows to 10 metres tall. Its upright inflorescences appear late in winter or early in spring, before the leaves. Later, its tiny flowers turn into remarkable chocolate-brown fruits, the size of a pea.
Here and there are small patches of subtropical forest, comprising e.g. chir pine, or long-leaved pine (Pinus roxburghii), and chestnuts of the genus Castanopsis, whose seeds are edible. (Read more about these two genera on this website, see Traditional medicine: Pinus roxburghii, and Castanopsis indica, respectively.) Many epiphytes adorn the trees, such as two species of mistletoe, Scurrula elata and Taxillus vestitus, and beautiful orchids of the genera Coelogyne and Dendrobium, the latter genus comprising no less than c. 26 species in the Himalaya.
On the forest floor, we observe bushes like Viburnum erubescens and Melastoma normale, the latter with beautiful reddish-violet flowers. Herbs include Cautleya gracilis, of the ginger family, and the peculiar Arisaema tortuosum, of the arum family. (More about this remarkable genus is found on this website, see Plant hunting in the Himalaya: Around sacred lakes of Shiva.) In a grass-covered area, we find tiny, star-shaped, yellow flowers of Hypoxis aurea. This small genus constitutes a family of its own, Hypoxidaceae, which is closely related to the amaryllis family (Amaryllidaceae).
From the village of Num, a steep trail leads through terraced fields and lush patches of forest down to the Arun River. The altitude here is a mere 700 metres, and the climate is hot and very humid – like in a Turkish bath. On the river bank, we observe an orchid, Dendrobium densiflorum, with a cluster of gorgeous yellow flowers. A suspension bridge brings us to the western bank, from where we make a long, tough hike up to the village of Tashigaon – the last, permanently inhabited village of the area. Along the terraced fields, we observe a number of weeds, such as goat-weed (Ageratum conyzoides), a tiny St. John’s wort, Hypericum japonicum, a dayflower, Commelina paludosa, with blue flowers, downy bur-marigold (Bidens pilosa), which has white flowers, and an everlasting, Gnaphalium affine, with yellow flowers.
A common climber is Holboellia latifolia, which belongs to a small Oriental plant family, Lardizabalaceae. Epiphytes include Rhododendron dalhousiae, which displays gorgeous, lemon-coloured flowers, which later turn yellowish-white, and a dwarf shrub, Agapetes serpens, whose amphora-shaped flowers are red with darker markings. A mat-forming wintergreen, Gaultheria trichophylla, grows on moss-covered rocks, easily identified by its almost luminous, blue berries, which are edible. (A picture of this species is found on this website, see Plant hunting in the Himalaya – Rainy season in Nepal.)
Herbs in this zone include two other Arisaema species, A. griffithii and A. costatum, a meadow-rue, Thalictrum virgatum, with rather large, white flowers, a pink primrose, Primula petiolaris, and Paris polyphylla, a close relative of the European herb Paris (Paris quadrifolia). From a rocky ridge near Kauma, we can enjoy a magnificent view towards Kangchendzonga, at 8,586 metres the third-highest mountain in the world.
To enter the Barun Valley, we must cross two passes north-west of Kauma, the highest of which, Keke La, is a mere 4,229 metres high. However, due to the topography of this area, precipitation is very high all winter, spring, and summer. For this reason, these passes are snow-covered until late June, and if you hike here without companions who know the way, you can easily get lost.
On our way towards the Barun Valley in late April, we saw no flowering plants at all at these heights, and even on our return journey three weeks later, only three species were blooming: Bergenia purpurascens, of the saxifrage family, a violet primrose, Primula calderiana, and a rare member of the primrose family, Omphalogramma elwesiana, for which these passes constitute a core area.
In the Barun Valley, the mountain slopes are covered in forest, chiefly of Himalayan silver fir (Abies spectabilis) and Himalayan birch (Betula utilis). Lower strata of the forest are often covered in a dense tangle of large shrubs, comprising various rhododendron species, such as R. hodgsonii, R. campylocarpum, and R. falconeri. Other rhododendron species, which we encounter on our hike, are smaller, e.g. R. fulgens, R. thomsonii, R. ciliatum, R. cinnabarinum, and R. wightii. These thickets are a fine habitat for the rare Himalayan musk deer, and also for the beautiful blood pheasant (Ithaginis cruentus), named after the tear-shaped, red streaks on the breast of the cock.
In May, herbs of the valley have only just begun to bloom. The beautiful pink Diapensia himalaica grows here and there, and we also observe Adonis nepalensis, which closely resembles the European spring adonis (A. vernalis), but is smaller. Other species include a cushion-forming saxifrage, Saxifraga pulvinaria, the yellow-flowered Corydalis govaniana, and a small violet primrose, Primula atrodentata. On the slopes grows a tiny dwarf shrub, Rhododendron pumilum, which is rather common in this valley, but is otherwise rare in Nepal.
At Neh, an ominous, black rockwall rises almost vertically from the valley floor. Here, the valley makes a sharp, ninety-degree turn towards west. We observe lammergeiers (Gypaetus barbatus), gliding effortlessly along the rock wall, searching for bones, which they carry high up in the air, letting them fall onto the rocks, after which they eat the marrow of the splintered bones. South of the valley is a towering, snow-covered mountain, Peak 7 (6185 m), from which a glacier, covered in moraine, slowly slides into the valley.
On the south-side of the valley, Peak 6 (6739 m) is towering towards the sky, whereas three other peaks, Chonku Chuli (6809 m), Baruntse (7220 m), and Peak 4 (6720 m) lie at the end of the valley. Small avalanches of snow and rocks constantly tumble into the valley from glaciers and mountain slopes.
The further west we go, the lower and more wind-blown are the juniper shrubs. In this harsh environment, we only find a few blooming herbs, two small gentians and a violet-flowered member of the mustard family. The major part of the valley floor is occupied by the huge Barun Glacier, the major part of it covered in eroded soil and rocks. West of a sandy plain, Merak, we head north, following a ridge, which ends on a tiny plateau, situated at an altitude of c. 5,300 metres. From here, we have a fantastic view towards numerous towering mountains, e.g. Makalu, Lhotse (8511 m), and Sagarmatha (8850 m).