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

evergreen In botany, an evergreen is a plant which has Leaf, foliage that remains green and functional throughout the year. This contrasts with deciduous plants, which lose their foliage completely during the winter or dry season. Consisting of many diffe ...

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

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Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...

Pakistan Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...

and

Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...

. It is the

national flower In a number of countries, plants have been chosen as symbols to represent specific geographic areas. Some countries have a country-wide floral emblem; others in addition have symbols representing subdivisions. Different processes have been used t ...

of Nepal. In India it is the state tree of

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and state flower of

Nagaland Nagaland () is a States and union territories of India, state in the northeast India, north-eastern 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 Naga Sel ...

Description

Its

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

means "tending to be woody or growing in a tree-like form". It has been recorded as reaching heights of , though it is more usually tall and broad. This plant holds the Guinness Record for the World's Largest Rhododendron. The tree discovered in 1993 at Mount Japfü in the Kohima District of

, India, holds the Guinness Record for the tallest Rhododendron at . In sharp contrast to this, the

New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; , fossilized , also known as Papua or historically ) is the List of islands by area, world's second-largest island, with an area of . Located in Melanesia in the southwestern Pacific Ocean, the island is ...

epiphytic An epiphyte is a plant or plant-like organism that grows on the surface of another plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphyt ...

species '' Rhododendron caespitosum'' never exceeds in height. 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 shrub ...

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

Subspecies

*''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 fa ...

, rhododendron and azalea

whiteflies Whiteflies are Hemipterans that typically feed on the undersides of plant leaves. They comprise the family Aleyrodidae, the only family in the superfamily Aleyrodoidea. More than 1550 species have been described. Description and taxonomy The A ...

leafhopper Leafhopper is the common name for any species from the family (biology), family Cicadellidae: based on the type genus ''Cicadella''. These minute insects, colloquially known as hoppers, are plant feeders that suck plant sap from grass, shrubs, or ...

s, lacebugs, scale insects,

caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder ...

aphid Aphids are small sap-sucking insects in the Taxonomic rank, family Aphididae. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white Eriosomatinae, woolly ...

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

, bud blast,

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

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(OH) ...

, leafy

gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants. Plant galls are abnormal outgrowths of plant tissues, similar to benign tumors or war ...

, petal

blight Blight is 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 organs. A ...

, 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