Rhododendron ponticum

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Rhododendron ponticum
Rhododendron ponticum ssp. baeticum in Cambarinho Botanical Reserve, Portugal.JPG
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Ericales
Family: Ericaceae
Genus: Rhododendron
Species:
R. ponticum
Binomial name
Rhododendron ponticum
L.
Synonyms [1]
List
    • Azalea arboreaL.
    • Azalea lancifolia(Moench) Kuntze
    • Hymenanthes pontica(L.) H.F.Copel.
    • Rhododendron adansoniiE.-A.Baumann
    • Rhododendron catesbaeiJ.Forbes
    • Rhododendron catesbaeumDum.Cours.
    • Rhododendron deciduumAndrews ex Steud.
    • Rhododendron hyacinthiflorumSteud.
    • Rhododendron lancifoliumMoench
    • Rhododendron loweiLoudon
    • Rhododendron obtusumP.Watson
    • Rhododendron odoratumLodd. ex Steud.
    • Rhododendron ponticum f. angustilobumRukhadze & Pachulia
    • Rhododendron ponticum f. aurantiacomaculatumRukhadze & Pachulia
    • Rhododendron ponticum f. brachystamineumRukhadze & Pachulia
    • Rhododendron ponticum f. crispatumRukhadze & Pachulia
    • Rhododendron ponticum f. luteomaculatumRukhadze & Pachulia
    • Rhododendron ponticum var. obtusum(P.Watson) G.Don
    • Rhododendron ponticum f. parviflorumRukhadze & Pachulia
    • Rhododendron speciosumSalisb.
R. ponticum flower Rhododendron-by-eiffel-public-domain-20040617.jpg
R. ponticum flower

Rhododendron ponticum, called common rhododendron or pontic rhododendron, is a species of flowering plant in the Rhododendron genus of the heath family Ericaceae. It is native to the Iberian Peninsula in southwest Europe and the Caucasus region in northern West Asia.

Contents

Description

R. ponticum is a dense, suckering shrub or small tree growing to 5 m (16 ft) tall, rarely 8 m (26 ft). The leaves are evergreen, 6 to 18 cm (2.4 to 7.1 in) long and 2 to 5 cm (0.79 to 1.97 in) wide. The flowers are 3.5 to 5 cm (1.4 to 2.0 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 (0.59 to 0.98 in) long, containing numerous small seeds.

It has two subspecies:

ImageNameDistribution
Rhododendron ponticum ssp baeticum.JPG R. p. baeticum (Boiss. & Reut.) Hand.-Mazz.Found in central and southern Portugal and southern Spain (in the Province of Cádiz). [2]
Strandzhanska zelenika Rhododendron ponticum.jpg R. p. ponticumFound around the southern Black Sea Basin (eastern Bulgaria, northern Turkey, Georgia, Northern Caucasus) and central Lebanon. [3]

And a variegated variety:

Distribution and habitat

The species has two disjunct populations, one in the southwestern Iberian Peninsula (central and southern Portugal and southwestern Spain) and the other near the southern Black Sea Basin (eastern Bulgaria, northern Turkey, Georgia, and Northern Caucasus). It has also been introduced to Madeira, Myanmar, Belgium, the British Isles, Netherlands and France. [1] [3]

The range in the Iberian Peninsula is limited to mountain ranges, the Caramulo mountains, the Monchique range and the Aljibe range. A remnant of the original laurissilva forests that covered the peninsula 66 million years ago. [5]

Though the common rhododendron was present in Great Britain prior to the most recent ice age, it did not recolonise afterwards and the modern ecology of the island developed without it. Its presence today in Great Britain is due to humans introducing it, and it easily naturalises and becomes a pest in some situations, often covering whole hillsides (especially in Snowdonia and the western Scotland). In the British Isles, it colonises moorlands, uplands, shady woodlands (alongside escaped laurels and the native holly) and in areas of acid soils. [6]

Historical range

Fossil 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. [6]

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.[ citation needed ] It was introduced to Britain as an ornamental shrub in 1763, and later planted as cover for game birds. It is now considered to be an invasive species. [7]

Cultivation and uses

Closeup of Rhododendron ponticum Rhododendron ponticum 2.jpg
Closeup of Rhododendron ponticum

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 18th and early 19th centuries. 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, and is known as mad honey due to toxic diterpenes (grayanotoxins). [8] This poisonous honey plays a significant part in the 2023 film A Haunting in Venice .

Sap from a freshly cut branch can be used to treat toothaches. [9]

Invasive species

Suckering of the root, together with its abundant seed production, has led to it becoming an invasive species over much of western Europe and in parts of New Zealand. Rhododendron control is a key element in nature conservation in those areas. [10] Conservation organisations in Britain now believe R. ponticum has become "a severe problem" in the native Atlantic oakwoods of the west highlands of Scotland and in Wales and Ireland, and on heathlands in southern England, crowding out the native flora. [11] 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. [12]

A study [13] in the journal Functional Ecology also showed that invasive rhododendron nectar was toxic to European honeybees ( Apis mellifera ), killing individuals within hours of consumption. It also paralyzed bees of the species Andrena carantonica , a solitary mining bee. Bees became paralysed and exhibited excessive grooming or other distress behaviours after feeding on Rhododendron nectar, and ate less food than bees fed a control nectar. In contrast the buff-tailed bumblebee ( Bombus terrestris ) was not affected by the rhododendron nectar. It is important not to see Rhododendron as a problem species for honey bees as they actually avoid the flowers owing to their ability to detect the toxin nectar. The toxicity is caused by grayanotoxin 1 which is one of several highly hydroxylated diterpenoid defence chemicals produced in the leaves of Rhododendron to protect against herbivores – e.g. the Thrips Heliothrips haemorrhoidalis. [14] Some species of honey bee (Apis mellifera sub spp caucasica) tolerate the toxin and make so-called "mad honey".

Identification difficulties

Recent efforts to manage the spread of Rhododendron ponticum in the United Kingdom has led to some controversy, particularly within the grounds of Taymouth Castle in highland Perthshire. There remains debate over appropriate identification of the plant, particularly where it is interspersed amongst clumps of Japanese laurel (Aucuba japonica) in areas of mixed woodland. Tensions surrounding the management of these cohabiting species were brought to a head in early December 2022 when prominent arboriculturalists faced strong opposition from machine operators within the estate over correct identification and subsequent management of the plant, culminating in the destruction of a large thicket of laurel. While there remains debate over the associated similarities and differences between the plants, contemporary research indicates the likelihood of a hybridisation between the two species in this niche of woodland, meaning that Japanese laurel may indeed be viewed and treated in a like manner to rhododendron within this habitat niche. [15]

See also

Related Research Articles

<i>Rhododendron</i> Genus of flowering plants in the heath family Ericaceae

Rhododendron is a very large genus of about 1,024 species of woody plants and in the heath family (Ericaceae). They can be either evergreen or deciduous. Most species are native to eastern Asia and the Himalayan region, but smaller numbers occur elsewhere in Asia, and in North America, Europe and Australia.

<span class="mw-page-title-main">Pollinator</span> Animal that moves pollen from the male anther of a flower to the female stigma

A pollinator is an animal that moves pollen from the male anther of a flower to the female stigma of a flower. This helps to bring about fertilization of the ovules in the flower by the male gametes from the pollen grains.

Grayanotoxins are a group of closely related neurotoxins named after Leucothoe grayana, a plant native to Japan and named for 19th-century American botanist Asa Gray. Grayanotoxin I is also known as andromedotoxin, acetylandromedol, rhodotoxin and asebotoxin. Grayanotoxins are produced by Rhododendron species and other plants in the family Ericaceae. Honey made from the nectar and so containing pollen of these plants also contains grayanotoxins and is commonly referred to as mad honey.

<i>Acer pseudoplatanus</i> Species of flowering plant in the lychee family Sapindaceae

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<i>Hedera</i> Genus of flowering plants in the family Araliaceae

Hedera, commonly called ivy, is a genus of 12–15 species of evergreen climbing or ground-creeping woody plants in the family Araliaceae, native to Western Europe, Central Europe, Southern Europe, Macaronesia, northwestern Africa and across central-southern Asia east to Japan and Taiwan. Several species are cultivated as climbing ornamentals, and the name ivy especially denotes common ivy, known in North America as "English ivy", which is frequently planted to clothe brick walls.

<i>Digitalis purpurea</i> Toxic flowering plant in the family Plantaginaceae

Digitalis purpurea, the foxglove or common foxglove, is a toxic species of flowering plant in the plantain family Plantaginaceae, native to and widespread throughout most of temperate Europe. It has also naturalized in parts of North America, as well as some other temperate regions. The plant is a popular garden subject, with many cultivars available. It is the original source of the heart medicine digoxin. This biennial plant grows as a rosette of leaves in the first year after sowing, before flowering and then dying in the second year. It generally produces enough seeds so that new plants will continue to grow in a garden setting.

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<i>Rhododendron luteum</i> Species of plant

Rhododendron luteum, the yellow azalea or honeysuckle azalea, is a species of flowering plant in the heath family Ericaceae, native to southeastern Europe and southwest Asia. In Europe, it occurs from southern Poland and Austria, south through the Balkans, and east to southern Russia; and in Asia, east to the Caucasus.

<i>Rhododendron catawbiense</i> Species of plant

Rhododendron catawbiense, with common names Catawba rosebay, Catawba rhododendron, mountain rosebay, purple ivy, purple laurel, purple rhododendron, red laurel, rosebay, rosebay laurel, is a species of Rhododendron native to the eastern United States, growing mainly in the southern Appalachian Mountains from West Virginia south to northern Alabama.

<span class="mw-page-title-main">Mad honey</span> Psychoactive type of honey containing grayanotoxins

Mad honey is honey that contains grayanotoxins. The dark, reddish honey is produced from the nectar and pollen of genus Rhododendron and has intoxicating effects.

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<i>Erysimum baeticum</i> Species of flowering plant

Erysimum baeticum is an annual to perennial herb endemic to some mountains in the SE of Spain. This species has two subspecies: Erysimum baeticum bastetanum is found only in the Sierra de Baza, inhabiting the subalpine pine forests, from 1500 to 2000 m. a.s.l.. Erysimum baeticum baeticum is a subspecies endemic to the eastern range of the Sierra Nevada, inhabiting subalpine shrublands. Both subspecies flower during late May thru early July, displaying up to one hundred showy purple flowers arranged in several short stalks.

<i>Rhododendron arboreum</i> Species of flowering plant

Rhododendron arboreum, the tree rhododendron, is an evergreen shrub or small tree with a showy display of bright red flowers. It is found in Bhutan, China, India, Myanmar, Nepal, Sri Lanka, Pakistan and Thailand. It is the national flower of Nepal. In India it is the state tree of Uttarakhand and state flower of Nagaland.

<span class="mw-page-title-main">Asian hornet</span> Species of insect

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<i>Rhododendron periclymenoides</i> Species of shrub

Rhododendron periclymenoides, the pink azalea or pinxter flower, is a species of shrub in the heath family Ericaceae. It is native to eastern North America, where it is widespread from Alabama to New Hampshire. It is often found in riparian areas, in wet to dry forests.

Psylliodes luridipennis, commonly known as the Lundy cabbage flea beetle or the bronze Lundy cabbage flea beetle, is a species of flea beetle endemic to the island of Lundy, where it lives and feeds upon the endemic Lundy cabbage. Along with the true weevil Ceutorhynchus contractus var. pallipes and an undescribed race of flea beetle Psylliodes napi, it is known only from the Lundy cabbage. The species was first recorded by Thomas Vernon Wollaston in the 1840s, and was named by the Austrian entomologist Franz Kutschera in 1864.

<i>Lyonia mariana</i> Species of shrub

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<i>Heliothrips haemorrhoidalis</i> Species of thrip

Heliothrips haemorrhoidalis is a species of thrips in the family Thripidae. It is most commonly known as the greenhouse thrips, the glasshouse thrip or black tea thrips. This species of thrips was first described in 1833 by Bouché in Berlin, Germany. H. haemorrhoidalis also has many synonyms depending on where they were described from such as: H. adonidum Haliday, H. semiaureus Girault, H. abdominalis Reuter, H. angustior Priesner, H. ceylonicus Schultz, Dinurothrips rufiventris Girault. In New Zealand, H. haemorrhoidalis is one of the four species belonging to the subfamily Panchaetothripinae.

<i>Euphorbia paniculata</i> Species of plant

Euphorbia paniculata is a species of flowering plant in the spurge family Euphorbiaceae, native to the Iberian Peninsula and North Africa in the western Mediterranean Basin.

References

  1. 1 2 "Rhododendron ponticum L." Plants of the World Online. Board of Trustees of the Royal Botanic Gardens, Kew. Retrieved 10 March 2024.
  2. "Infraspecific Taxon Details : Rhododendron ponticum subsp. baeticum (Boiss. & Reuter) Hand.-Mazz". Catalogue of Life . Retrieved 21 November 2020.
  3. 1 2 "Infraspecific Taxon Details : Rhododendron ponticum subsp. ponticum". Catalogue of Life . Retrieved 21 November 2020.
  4. "Infraspecific Taxon Details : Rhododendron ponticum var. heterophyllum R. Ansin". Catalogue of Life . Retrieved 21 November 2020.
  5. "A adelfeira de Monchique". University of Évora. 13 March 2018. Retrieved 21 November 2020.
  6. 1 2 Cross, JR (1975). "Rhododendron ponticum L.". Journal of Ecology. 63 (1): 345–364.
  7. Alice M. Coats, Garden Shrubs and Their Histories (1964) 1992, s.v. "Rhododendron"; http://www.countrysideinfo.co.uk/rhododen.htm#Introduction%20to%20Britain .
  8. Hayes, Andrew Wallace (2007). Principles and methods of toxicology. CRC Press. p. 998. ISBN   978-0-8493-3778-9.
  9. Erdemoglu, Nurgun; Akkol, Esra Küpeli; Yesilada, Erdem; Calış, Ihsan (2008-09-02). "Bioassay-guided isolation of anti-inflammatory and antinociceptive principles from a folk remedy, Rhododendron ponticum L. leaves". Journal of Ethnopharmacology. 119 (1): 172–178. doi:10.1016/j.jep.2008.06.021. ISSN   0378-8741. PMID   18638535.
  10. "New flora and fauna for old". The Economist. 2000-12-21. Archived from the original on 2001-07-28. Retrieved 2008-12-14.
  11. "Rhododendron: A killer of the Countryside". Offwell Woodland & Wildlife Trust. 2004. Retrieved 30 May 2010.
  12. "BREAKTHROUGH IN BATTLE AGAINST PROBLEM PONTICUM". Forestry Commission. 30 July 2004. Archived from the original on 5 March 2011. Retrieved 30 May 2010.
  13. Tiedeken, Erin Jo; Egan, Paul A.; Stevenson, Philip C.; Wright, Geraldine A.; Brown, Mark J. F.; Power, Eileen F.; Farrell, Iain; Matthews, Sharon M.; Stout, Jane C.; Manson, Jessamyn (November 2015). "Nectar chemistry modulates the impact of an invasive plant on native pollinators" (PDF). Functional Ecology. 30 (6): 885–893. doi: 10.1111/1365-2435.12588 .
  14. Scott-Brown, AS, Gregory, T, Farrell, IW, Stevenson PC. (2016). "Leaf trichomes and foliar chemistry mediate defence against glasshouse thrips; Heliothrips haemorrhoidalis (Bouché) in Rhododendron simsii". Functional Plant Biology. 43 (12): 1170–1182. doi:10.1071/FP16045. PMID   32480536.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  15. Milne, R.I. and Abbott, R.J., 2000. Origin and evolution of invasive naturalized material of Rhododendron ponticum L. in the British Isles. Molecular Ecology, 9(5), pp. 541–556.