''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, which ...

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 mountainous ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

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 ...

Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John C. Wells, Joh ...

Nepal Nepal (; ne, नेपाल ), formerly the Federal Democratic Republic of Nepal ( ne, सङ्घीय लोकतान्त्रिक गणतन्त्र नेपाल ), is a landlocked country in South Asia. It is mai ...

Sri Lanka Sri Lanka (, ; si, ශ්‍රී ලංකා, Śrī Laṅkā, translit-std=ISO (); ta, இலங்கை, Ilaṅkai, translit-std=ISO ()), formerly known as Ceylon and officially the Democratic Socialist Republic of Sri Lanka, is an ...

Pakistan Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...

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 bo ...

. 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 to ...

. In

it is the

state tree This is a list of U.S. state, federal district, and territory trees, including official trees of the following of the states, of the federal district, and of the territories. Table See also * List of U.S. state, district, and territorial insign ...

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 This is a list of U.S. state, federal district, and territory flowers. See also *List of U.S. state trees * Lists of U.S. state insignia References External linksList of state flowers {{USStateLists * U.S. state flowers Flowers ...

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 In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

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 List of districts of Nagaland, district of the Indian state of Nagaland. It is the home of the Angami Naga, Angami Naga people, Nagas. As of 2011, it is the second most populous district of Nagaland (out of then-List of d ...

, 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 shrub ...

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 Taxonomic rank, superfamily Curculionoidea, known for their elongated snouts. They are usually small, less than in length, and Herbivore, herbivorous. Approximately 97,000 species of weevils are known. They b ...

, 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 ...

leafhopper A leafhopper is the common name for any species from the family Cicadellidae. These minute insects, colloquially known as hoppers, are plant feeders that suck plant sap from grass, shrubs, or trees. Their hind legs are modified for jumping, and a ...

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,

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 Sym ...

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, as ...

bud blast In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of a stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately. Buds may be specia ...

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(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, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to be ...

, 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 organ ...

, 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

{{Taxonbar, from=Q2659683 arboreum Holarctic flora Flora of the Indian subcontinent Plants used in Ayurveda National symbols of Nepal Symbols of Nagaland Symbols of Uttarakhand Trees of Nepal Trees of Bhutan Flora of Bhutan