''Rhododendron arboreum'', the tree rhododendron, is an

evergreen In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, whic ...

shrub or small tree with a showy display of bright red flowers. It is found in

Bhutan Bhutan (; dz, འབྲུག་ཡུལ་, Druk Yul ), officially the Kingdom of Bhutan,), is a landlocked country in South Asia. It is situated in the Eastern Himalayas, between China in the north and India in the south. A mountainou ...

, China,

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

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Nepal Nepal (; ne, :ne:नेपाल, नेपाल ), formerly the Federal Democratic Republic of Nepal ( ne, सङ्घीय लोकतान्त्रिक गणतन्त्र नेपाल ), is a landlocked country in S ...

, Sri Lanka,

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and

Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...

. It is the national flower of

. In

it is the state tree of

Uttarakhand Uttarakhand ( , or ; , ), also known as Uttaranchal ( ; the official name until 2007), is a state in the northern part of India. It is often referred to as the "Devbhumi" (literally 'Land of the Gods') due to its religious significance and ...

and state flower of

Nagaland Nagaland () is a landlocked state in the northeastern region of India. It is bordered by the Indian states of Arunachal Pradesh to the north, Assam to the west, Manipur to the south and the Sagaing Region of Myanmar to the east. Its capital cit ...

Description

Its specific epithet means "tending to be woody or growing in a tree-like form". It has been recorded as reaching heights of , though more usually tall and broad. This plant holds the

Guinness Record ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a reference book published annually, listing world ...

for World's Largest Rhododendron. The tree discovered in 1993 at

Mount Japfü Mount Japfü (, ), is a mountain peak of the Barail Range, located in Kohima District Kohima District () is a district of the Indian state of Nagaland. It is the home of the Angami Nagas. As of 2011, it is the second most populous district of ...

in the

Kohima District Kohima District () is a district of the Indian state of Nagaland. It is the home of the Angami Nagas. As of 2011, it is the second most populous district of Nagaland (out of then- 12, now 16), after Dimapur with a population of 267,988, 45% of ...

, holds the Guinness Record for the tallest Rhododendron at . In early- and mid-spring, trusses of 15–20 bell-shaped flowers, wide and long are produced in red, pink or white. They have black nectar pouches and black spots inside.

Cultivation

''Rhododendron arboreum'' prefers moist but well-drained, leafy, humus-rich, acid pH soil, in dappled shade. It has broad, dark green leaves, long, with a silvery, fawn or brown hairy coating beneath. This plant is suitable for

woodland garden A woodland garden is a garden or section of a garden that includes large trees and is laid out so as to appear as more or less natural woodland, though it is often actually an artificial creation. Typically it includes plantings of flowering shru ...

s. Shelter is imperative to prevent wind damage to leaves.

Variants

*''Rhododendron arboreum'' subsp. ''cinnamomeum'' has leaves with cinnamon-brown hairs beneath * Flower of Rhododendron

''Rhododendron arboreum'' subsp. ''zeylanicum'' rare ssp from the highlands of Sri Lanka, named after Zeilan, the name used by Arabian traders to refer to Sri Lanka *''Rhododendron arboreum'' subsp. ''cinnamomeum'' var. ''album'' has white flowers with small blood red spots on the inner surface of the petals *''Rhododendron arboreum'' subsp. ''delavayi'' has red flowers *''Rhododendron arboreum'' subsp. ''nilagiricum'' (Zenker) Tagg is found in Tamil Nadu, India.

Threats

Rhododendrons are susceptible to vine

weevil Weevils are beetles belonging to the superfamily Curculionoidea, known for their elongated snouts. They are usually small, less than in length, and herbivorous. Approximately 97,000 species of weevils are known. They belong to several families, ...

, rhododendron and azalea whiteflies, leafhoppers,

lacebug The Tingidae are a family of very small () insects in the order Hemiptera that are commonly referred to as lace bugs. This group is distributed worldwide with about 2,000 described species. They are called lace bugs because the pronotum and for ...

s, scale insects, caterpillars,

aphid Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...

powdery mildew Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of ascomycete fungi in the order Erysiphales. Powdery mildew is one of the easier plant diseases to identify, a ...

, bud blast,

honey fungus ''Armillaria'' is a genus of fungi that includes the '' A. mellea'' species known as honey fungi that live on trees and woody shrubs. It includes about 10 species formerly categorized summarily as ''A. mellea''. ''Armillarias'' are long-l ...

rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO( ...

, leafy gall, petal

blight Blight refers to a specific symptom affecting plants in response to infection by a pathogenic organism. Description Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral org ...

, silver leaf, phytophthora root rot and lime-induced

chlorosis In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

.The Royal Horticultural Society (2008) ''RHS Garden Hyde Hall Plant of the month: April'', retrieved 2/19/200
Gardens

In Sri Lanka

The plant is known as Maha ratmal, Maha Rath Mal, Asela mal in Sinhala. The Sinhalese name "rathmal" is mostly used for the ''Ixoras'', which are not in this family. However, the Rhododendrons are not a common plant in Sri Lanka, and the unsystematic local name seems to be"Maha-rathmal", i.e., "Big-Ixora", applied to smaller varieties which are more like ornamental Azelias. Maha Rath Mala is commonly available in Horton Plain, Knuckles mountain range and many of the parts towards the center of Sri Lanka.

References