Rhododendron ponticum
Encyclopedia
Rhododendron ponticum, called Common Rhododendron or Pontic Rhododendron, is a species of Rhododendron
native to southern Europe
and southwest Asia
.
or small tree
growing to 5 m (16.4 ft) tall, rarely 8 m (26.2 ft). The leaves
are evergreen
, 6 to 18 cm (2.4 to 7.1 in) long and 2 to 5 cm (0.78740157480315 to 2 in) wide. The flower
s are 3.5 to 5 cm (1.4 to 2 in) in diameter, violet-purple, often with small greenish-yellow spots or streaks. The fruit
is a dry capsule
1.5 to 2.5 cm (0.590551181102362 to 0.984251968503937 in) long, containing numerous small seed
s.
There are two subspecies
:
, northern Portugal
, Great Britain
, Ireland
and southeast Bulgaria
, which is the last surviving European Tertiary habitat.
In Asia it occurs in Turkey
, Lebanon
, Georgia
, the Krasnodar
area of southern Russia
, the Himalayas
, Afghanistan
, Tajikistan
, Northern Pakistan, and northern India
.
evidence shows it had a much wider range across most of southern and western Europe before the Late Glacial Maximum, or until about 20,000 years ago.
It was noted by the botanist Joseph Pitton de Tournefort
during his travels in the Near East in 1700-02, and so received its name from Linnaeus to identify the ancient kingdom on the south shores of the Black Sea
, Pontus
, in which it grew. At the other end of its range, in southern Spain, Linnaeus' friend and correspondent Clas Alströmer
found it growing with Oleander
. It was introduced to Britain as an ornamental shrub
in 1763, where it is now considered by some to be an invasive species
.
Rhododendron ponticum subsp. baeticum is one of the most extensively cultivated rhododendrons in western Europe. It is used as an ornamental plant
in its own right, and more frequently as a rootstock
onto which other more attractive rhododendrons are grafted
. The plants were first grown in Britain in the 1760s, supplied by Conrad Loddiges
and became widely distributed through the commercial nursery trade in the late C18th and early c19th. The roots readily send up suckers from below the graft, often allowing it to overtake the intended grafted rhododendron.
Honey produced with pollen from the flowers of this plant can be quite poisonous, causing severe hypotension
and bradycardia
in humans if consumed in sufficient quantities, due to toxic diterpenes (Grayanotoxin
s).
over much of western Europe and in parts of New Zealand
. Rhododendron control, or rhodie-bashing, is a key element in nature conservation in those areas.
Conservation organisations in Britain now believe that R.ponticum has become "a severe problem" in the native Atlantic oak
woods of the west highlands
of Scotland
and in Wales
, and on heathlands in southern England
, crowding out the native flora. Clearance strategies have been developed, including the flailing and cutting down of plants with follow-up herbicide
spraying. Injection of herbicide into individual plants has been found to be more precise and effective.
Rhododendron
Rhododendron is a genus of over 1 000 species of woody plants in the heath family, most with showy flowers...
native to southern Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and southwest Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
.
Description
Rhododendron ponticum is a dense, suckering shrubShrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
or small tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
growing to 5 m (16.4 ft) tall, rarely 8 m (26.2 ft). The leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
are evergreen
Evergreen
In botany, an evergreen plant is a plant that has leaves in all seasons. This contrasts with deciduous plants, which completely lose their foliage during the winter or dry season.There are many different kinds of evergreen plants, both trees and shrubs...
, 6 to 18 cm (2.4 to 7.1 in) long and 2 to 5 cm (0.78740157480315 to 2 in) wide. The flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s are 3.5 to 5 cm (1.4 to 2 in) in diameter, violet-purple, often with small greenish-yellow spots or streaks. The fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
is a dry capsule
Capsule (fruit)
In botany a capsule is a type of simple, dry fruit produced by many species of flowering plants. A capsule is a structure composed of two or more carpels that in most cases is dehiscent, i.e. at maturity, it splits apart to release the seeds within. A few capsules are indehiscent, for example...
1.5 to 2.5 cm (0.590551181102362 to 0.984251968503937 in) long, containing numerous small seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
s.
There are two subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
:
- Rhododendron ponticum subsp. ponticum. Bulgaria east to Georgia.
- Rhododendron ponticum subsp. baeticum (Boiss. & Reut.) Hand.-Mazz. Spain, Portugal.
Range
In Europe, its range includes SpainSpain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
, northern Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
, Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
, Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
and southeast Bulgaria
Bulgaria
Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...
, which is the last surviving European Tertiary habitat.
In Asia it occurs in Turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...
, Lebanon
Lebanon
Lebanon , officially the Republic of LebanonRepublic of Lebanon is the most common term used by Lebanese government agencies. The term Lebanese Republic, a literal translation of the official Arabic and French names that is not used in today's world. Arabic is the most common language spoken among...
, Georgia
Georgia (country)
Georgia is a sovereign state in the Caucasus region of Eurasia. Located at the crossroads of Western Asia and Eastern Europe, it is bounded to the west by the Black Sea, to the north by Russia, to the southwest by Turkey, to the south by Armenia, and to the southeast by Azerbaijan. The capital of...
, the Krasnodar
Krasnodar
Krasnodar is a city in Southern Russia, located on the Kuban River about northeast of the Black Sea port of Novorossiysk. It is the administrative center of Krasnodar Krai . Population: -Name:...
area of southern Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
, the Himalayas
Himalayas
The Himalaya Range or Himalaya Mountains Sanskrit: Devanagari: हिमालय, literally "abode of snow"), usually called the Himalayas or Himalaya for short, is a mountain range in Asia, separating the Indian subcontinent from the Tibetan Plateau...
, Afghanistan
Afghanistan
Afghanistan , officially the Islamic Republic of Afghanistan, is a landlocked country located in the centre of Asia, forming South Asia, Central Asia and the Middle East. With a population of about 29 million, it has an area of , making it the 42nd most populous and 41st largest nation in the world...
, Tajikistan
Tajikistan
Tajikistan , officially the Republic of Tajikistan , is a mountainous landlocked country in Central Asia. Afghanistan borders it to the south, Uzbekistan to the west, Kyrgyzstan to the north, and China to the east....
, Northern Pakistan, and northern India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
.
History
FossilFossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
evidence shows it had a much wider range across most of southern and western Europe before the Late Glacial Maximum, or until about 20,000 years ago.
It was noted by the botanist Joseph Pitton de Tournefort
Joseph Pitton de Tournefort
Joseph Pitton de Tournefort was a French botanist, notable as the first to make a clear definition of the concept of genus for plants.- Biography :...
during his travels in the Near East in 1700-02, and so received its name from Linnaeus to identify the ancient kingdom on the south shores of the Black Sea
Black Sea
The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...
, Pontus
Pontus
Pontus or Pontos is a historical Greek designation for a region on the southern coast of the Black Sea, located in modern-day northeastern Turkey. The name was applied to the coastal region in antiquity by the Greeks who colonized the area, and derived from the Greek name of the Black Sea: Πόντος...
, in which it grew. At the other end of its range, in southern Spain, Linnaeus' friend and correspondent Clas Alströmer
Clas Alströmer
Baron Clas Alströmer was a Swedish naturalist who was a student of Carl Linnaeus at Uppsala University. From 1760–1764 he traveled throughout Southern Europe, collecting plants for Linnaeus. He established a botanical garden and natural museum near Gothenburg which was managed by the notable...
found it growing with Oleander
Oleander
Nerium oleander is an evergreen shrub or small tree in the dogbane family Apocynaceae, toxic in all its parts. It is the only species currently classified in the genus Nerium. It is most commonly known as oleander, from its superficial resemblance to the unrelated olive Olea, but has many other...
. It was introduced to Britain as an ornamental shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
in 1763, where it is now considered by some to be an invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
.
Cultivation and uses
Ornamental plant
Ornamental plants are plants that are grown for decorative purposes in gardens and landscape design projects, as house plants, for cut flowers and specimen display...
in its own right, and more frequently as a rootstock
Rootstock
A rootstock is a plant, and sometimes just the stump, which already has an established, healthy root system, used for grafting a cutting or budding from another plant. The tree part being grafted onto the rootstock is usually called the scion...
onto which other more attractive rhododendrons are grafted
Grafting
Grafting is a horticultural technique whereby tissues from one plant are inserted into those of another so that the two sets of vascular tissues may join together. This vascular joining is called inosculation...
. The plants were first grown in Britain in the 1760s, supplied by Conrad Loddiges
Loddiges
The Loddiges family managed one of the most notable of the eighteenth and nineteenth century plant nurseries that traded in and introduced exotic plants, trees, shrubs, ferns, palms and orchids into European gardens....
and became widely distributed through the commercial nursery trade in the late C18th and early c19th. The roots readily send up suckers from below the graft, often allowing it to overtake the intended grafted rhododendron.
Honey produced with pollen from the flowers of this plant can be quite poisonous, causing severe hypotension
Hypotension
In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
and bradycardia
Bradycardia
Bradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...
in humans if consumed in sufficient quantities, due to toxic diterpenes (Grayanotoxin
Grayanotoxin
Grayanotoxins are a group of closely related toxins found in rhododendrons and other plants of the family Ericaceae. They can be found in honey made from their nectar and cause a very rare poisonous reaction called grayanotoxin poisoning, honey intoxication, or rhododendron poisoning...
s).
Invasive species
Suckering of the root, together with its abundant seed production, has led to it becoming an invasive speciesInvasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
over much of western Europe and in parts of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. Rhododendron control, or rhodie-bashing, is a key element in nature conservation in those areas.
Conservation organisations in Britain now believe that R.ponticum has become "a severe problem" in the native Atlantic oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
woods of the west highlands
Scottish Highlands
The Highlands is an historic region of Scotland. The area is sometimes referred to as the "Scottish Highlands". It was culturally distinguishable from the Lowlands from the later Middle Ages into the modern period, when Lowland Scots replaced Scottish Gaelic throughout most of the Lowlands...
of Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
and in Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
, and on heathlands in southern England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, crowding out the native flora. Clearance strategies have been developed, including the flailing and cutting down of plants with follow-up herbicide
Herbicide
Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...
spraying. Injection of herbicide into individual plants has been found to be more precise and effective.
External links
- Flora Europaea: Rhododendron ponticum
- Rhododendron Ponticum is the emblem and symbol of Bulgaria's most exotic National Park - The Strandja mountains
- Germplasm Resources Information Network: Rhododendron ponticum
- Centre for Conservation Strategy: Rhododendron ponticum in Britain
- Milne, R. I., & Abbott, R. J. (2000). Origin and evolution of invasive naturalized material of Rhododendron ponticum L. in the British Isles. Molecular Ecology 9: 541-556 Abstract.