Shown here is the traditional classification, with species number after Chamberlain (1996), but this scheme is undergoing constant revision.  The centres of diversity are in the Himalayas and Malaysia, with the greatest species diversity in the Sino-Himalayan region, Southwest China and northern Burma, from Himachal Pradesh, Uttarakhand, Nepal, Sikkim, Nagaland to northwestern Yunnan and western Sichuan and southeastern Tibet. November 25, 2020. Rhododendrons range in size from dwarf shrubs to medium-sized trees. Red-flowered varieties such as Baden Baden (Rhododendron 'Baden Baden') and Scarlet Wonder (Rhododendron 'Scarlet Wonder') stay small and are hardy down to USDA zone 6. , Rhododendrons are extensively hybridized in cultivation, and natural hybrids often occur in areas where species ranges overlap. Rhododendron arboreum is also the state tree of the state of Uttarakhand, India. Information on Rhododendrons by Marc Colombel, founder of the Société Bretonne du Rhododendron. The species in New Guinea are native to subalpine moist grasslands at around 3,000 metres above sea level in the Central Highlands. 10 Varieties of Rhododendrons to Try in Your Yard (+ Growing Tips) Looking for an evergreen shrub that loves the shade, bears large flowers, is low maintenance and will last for decades? Plant in spring or early fall. People have been known to become ill from eating honey made by bees feeding on rhododendron and azalea flowers. Rhododendrons (Rhododendron spp.) This division was based on a number of what were thought to be key morphological characteristics. On Rhododendron leucaspis the flowers are small bells and it's the bell form which is typical of Rhododendrons. Terminology from the Sleumer (1949) system is frequently found in older literature, with five subgenera and is as follows; In the later traditional classification, attributed to Chamberlain (1996), and as used by horticulturalists and the American Rhododendron Society, Rhododendron has eight subgenera based on morphology, namely the presence of scales (lepidote), deciduousness of leaves, and the floral and vegetative branching patterns, after Sleumer (1980). , In Daphne Du Maurier's novel Rebecca, the character of Rebecca is associated with "blood red" rhododendrons throughout the novel, perhaps due to the toxic roots of the plant mirroring the poisonous character of Rebecca. How to choose the substrate for growing in pots. Keys to Not Killing Your Rhododendron 1. Some hybrids have fragrant flowers—such as the Loderi hybrids, created by crossing Rhododendron fortunei and R. giganteum, reported to 30 m (100 ft) tall. The industry is promoted by the state government with tax benefits, looking to promote this industry as a full-fledged subclass of its economy. The fastest-growing rhododendron cultivars grow 7 feet in 10 years, according to the American Rhododendron … The first two subgenera (Rhododendron and Hymenanthes) represent the species commonly considered as 'Rhododendrons'.  Many species and cultivars are grown commercially for the nursery trade. While usually grown as shrubs, they can get very big and take up the space of a small tree. Both species and hybrid rhododendrons (including azaleas) are used extensively as ornamental plants in landscaping in many parts of the world, including both temperate and subtemperate regions. , Rhododendron bud blast, a fungal condition that causes buds to turn brown and dry, and not open, is caused by the fungus Pycnostysanus azaleae, which may be brought to the plant by the rhododendron leafhopper, Graphocephala fennahi.(p562).  In 1987 Spethmann, adding phytochemical features proposed a system with fifteen subgenera grouped into three 'chorus' subgenera. Individual hybrids of rhododendrons have been grafted on to a rootstock on a single rhododendron plant that was found growing in a chalk quarry. Sleumer based his system on the relationship of the flower buds to the leaf buds, habitat, flower structure, and whether the leaves were lepidote or non-lepidote. They thrive in a moist, well-drained, humus-filled soil with a pH of 5.0 to 6.0, enriched with peat moss or leaf mold. , Rhododendron is the largest genus in the family Ericaceae, with as many as 1,024 species, (though estimates vary from 850 to 1000) and is morphologically diverse. The pot’s size is also important, it shouldn’t be too big. Eleven similar cases have been documented in Istanbul, Turkey during the 1980s. Yes, it does! Plant Hardiness Zones 4-8 . Growing rhododendron successfully requires the proper planting spot for the rhododendron bush. giganteum, reported to 30 m (100 ft) tall. Rhododendrons are stunning bushes that produce big, beautiful blossoms in the spring (and in the case of some varieties again in the fall). They may be either evergreen or deciduous. They like moist, rather cool air. Rhododendron is a genus of shrubs and small to (rarely) large trees, the smallest species growing to 10–100 cm (4–40 in) tall, and the largest, R. protistum var. Miniature rhododendrons seldom grow beyond a foot in height.  The largest of these is subgenus Rhododendron, containing nearly half of all known species and all of the lepidote species. As new species of what are now considered Rhododendron were discovered, if they seemed to differ significantly from the type species they were assigned to separate genera. , The 300 tropical species within the Vireya section of subgenus Rhododendron occupy the Malay archipelago from their presumed Southeast Asian origin to Northern Australia, with 55 known species in Borneo and 164 in New Guinea. Soil preparation is best accomplished in autumn before planting the rhododendron in spring. The world's most glorious rhododendrons grow in Seattle, Ireland, England, New Zealand, and other places in the Goldilocks zone where it's not too hot, not too cold, but just right. They like well drained acid soil. They can be planted by themselves but are also attractive when planted in groups. Rhododendrons are often valued in landscaping for their structure, size, flowers, and the fact that many of them are evergreen. When it comes to the Lavender Rhododendron, there's nothing you can't do. Maximovicz used flower bud position and its relationship with leaf buds to create eight "Sections". Unfortunately, most rhododendrons and azaleas (there are over 900 species and innumerable varieties) cannot be successfully grown in Iowa because of a lack of cold hardiness. Quick facts. We don't live there. Mother of Pearl (Rhododendron 'Mother of Pearl') and Mount Everest (Rhododendron 'Mount Everest') both bear white flowers and are hardy down to USDA zone 6. Rhododendron borers and various weevils are major pests of rhododendrons, and many caterpillars will preferentially devour them. Linnaeus' six species of Azalea were Azalea indica, A. pontica, A. lutea, A. viscosa, A. lapponica and A. procumbens (now Kalmia procumbens), which he distinguished from Rhododendron by having five stamens, as opposed to ten. Varieties hardy only to USDA zone 7 can't tolerate extended cold spells, and include varieties such as Cappuccino (Rhododendron 'Cappuccino') and September Snow (Rhododendron 'September Snow'), both bearing white flowers, and Primary Pink (Rhododendron 'Primary Pink'), which bears pink flowers. Rhododendron species are used as food plants by the larvae (caterpillars) of some butterflies and moths; see List of Lepidoptera that feed on rhododendrons. Major diseases include Phytophthora root rot, stem and twig fungal dieback; Ohio State University Extension provides information on maintaining health of rhododendrons. Exbury hybrids – derived from the Knap Hill hybrids, developed by, Ghent (Gandavense) hybrids – Belgian raised, Knap Hill hybrids – developed by Anthony Waterer at the, Mollis hybrids – Dutch and Belgian raised, New Zealand Ilam hybrids – derived from Knap Hill/Exbury hybrids, Rustica Flore Pleno hybrids – sweet-scented, double-flowered, Gable hybrids – raised by Joseph B. Gable in, Glenn Dale hybrids – US raised complex hybrids, Indian (Indica) hybrids – mostly of Belgian origin, Kyushu hybrids – very hardy Japanese azaleas (to −30 °C), Oldhamii hybrids – dwarf hybrids raised at, Satsuki hybrids – Japanese raised, originally for, Vuyk (Vuykiana) hybrids – raised in the Netherlands, Azaleodendrons – semi-evergreen hybrids between deciduous azaleas and rhododendrons, This page was last edited on 13 December 2020, at 21:10. They do like sun, but not full or bright sun. (2005) Table 1.. In all, Hymenanthes increased from one to two sections, while Azaleastrum, by losing one section and gaining two increased from two to three sections. Many of our competitors only offer smaller sizes, which will take years to reach an appealing height. , In the language of flowers, the Rhododendron symbolizes danger and to beware.. This genus has been progressively subdivided into a hierarchy of subgenus, section, subsection, and species. Rhododendrons can become quite large, even tree-like. Pink-flowered varieties include Furnival's Daughter (Rhododendron 'Furnival's Daughter') and Van (Rhododendron 'Van'), which are hardy down to USDA zone 6. R. ponticum is the state flower of Indian-administered Kashmir and Pakistan-controlled Kashmir. , They have frequently been divided based on the presence or absence of scales on the abaxial (lower) leaf surface (lepidote or elepidote). The rhododendron bush is an attractive, blooming specimen in many landscapes and is fairly low maintenance when planted properly. While Sleumer's work was widely accepted, many in the United States and the United Kingdom continued to use the simpler Balfourian system of the Edinburgh group. Proper soil preparation is also necessary for the health of this acid loving plant. Sometimes plants survive in spite of our treating them poorly. Rhododendron in botanical garden Pruhonice-Czech republic, Annotated Checklist of the Flowering Plants of Nepal: Rhododendron, The Quarterly Bulletin of the American Rhododendron Society 1947–1981, Journal of the American Rhododendron Society (JARS) 1982–, The Rhododendron, Camellia & Magnolia Group of the Royal Horticultural Society, Rhododendron Species Foundation and Botanical Garden, Royal Botanic Garden Edinburgh: Rhododendrons at the four Gardens, National Rhododendron Gardens Melbourne Australia, https://en.wikipedia.org/w/index.php?title=Rhododendron&oldid=994047924, Plants used in traditional Chinese medicine, Articles containing Ancient Greek (to 1453)-language text, Short description is different from Wikidata, Articles with unsourced statements from June 2020, Articles with unsourced statements from May 2016, Creative Commons Attribution-ShareAlike License. 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