How to grow rhododendrons. The first two subgenera (Rhododendron and Hymenanthes) represent the species commonly considered as 'Rhododendrons'. , Horticulturally, rhododendrons may be divided into the following groups:. Rhododendrons that stand 1 to 3 feet tall are often considered dwarfs. In addition, rhododendrons can easily be suffocated by other plants or evergreen trees that grow up around them and block sunlight. Miniature rhododendrons seldom grow beyond a foot in height. Many gardeners think azaleas and rhododendrons prefer to grow in deep shade.  The suspect rhododendrons are Rhododendron ponticum and Rhododendron luteum (formerly Azalea pontica), both found in northern Asia Minor. The next two smaller subgenera (Pentanthera and Tsutsusi) represent the 'Azaleas'.  Then Judd & Kron moved two species (Rhododendron schlippenbachii, R. quinquefolium) from section Brachybachii, subgenus Tsutsusi and two from section Rhodora, subgenus Pentanthera (R. albrechtii, R. pentaphyllum) into section Sciadorhodion, subgenus Pentanthera. Genus of flowering plants in the heath family Ericaceae, International Code of Botanical Nomenclature, List of Lepidoptera that feed on rhododendrons, List of Award of Garden Merit rhododendrons, List of Sections in Subgenus Rhododendron, "Sorting out the Genus Rhododendron: A Taxonomic Overview of this Large Complex of Species", "GROPING FOR GROUPING: Rhododendron Taxonomy", "The History of Vireya Rhododendron Culture", "Economic history: Farm-gardening and market gardening", "Infrageneric and Sectional Relationships in the Genus Rhododendron (Ericaceae) Inferred from ITS Sequence Data", "Excerpts from and comments on a paper published by: Loretta Goetsch, Andrew Eckert and Benjamin Hall, University of Washington", "Concerning the Origin and Distribution of Rhododendrons", "Dramatic rescue of couple trapped in rhododendron forest", "Maintaining Healthy Rhododendrons and Azaleas in the Landscape", "India has a 'wine country'? The major finding of Goetsch and colleagues was that all species examined (except R. camtschaticum, subgenus Therorhodion) formed three major clades which they labelled A, B and C, with the subgenera Rhododendron and Hymenanthes nested within clades A and B as monophyletic groups respectively. Broadcast: Sat 5 Oct 2013, … Rhododendrons are originally a woodland plant and so dappled shade is their native conditions, although Rhododendrons are fairly tough and will grow anywhere in the right (acid) soil. Choose heat-tolerant kinds. On Rhododendron leucaspis the flowers are small bells and it's the bell form which is typical of Rhododendrons. Some of the best known species are noted for their many clusters of large flowers. Soil preparation is best accomplished in autumn before planting the rhododendron in spring. They can get real big. Thus two subgenera, Hymenanthes and Azaleastrum were expanded at the expense of four subgenera that were eliminated, although Azaleastrum lost one section (Choniastrum) as a new subgenus, since it was a distinct subclade in A. We don't live there. Some hybrids have fragrant flowers—such as the Loderi hybrids, created by crossing Rhododendron fortunei and R. Rhododendron arboreum (lali guransh) is the national flower of Nepal. Remember, though, that many rhododendrons can grow from 20 to 30 feet tall, weaving a root system that spreads wider than the top growth, so moving smaller azaleas might be more successful. All need some sun for best flowering but in general require partial shade. Some may be small enough to place at the front of the border. More than 90% of Rhododendron sensu Chamberlain belong to the Asian subgenera Rhododendron, Hymenanthes and section Tsutsusi. It is the national flower of Nepal, the state flower of Washington and West Virginia in the United States, the provincial flower of Jiangxi in China and the state tree of Sikkim and Uttarakhand in India. Some are in big … 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? There are over 800 species of rhododendrons ranging from spreading groundcovers a few inches high to 100 foot tall trees and many thousands of registered, named varieties. The discontinued subgenera are Pentanthera, Tsutsusi, Candidastrum and Mumeazalea, while a new subgenus was created by elevating subgenus Azaleastrum section Choniastrum to subgenus rank. How to Plant Rhododendron & Azaleas. Like this rhododendron. ", "Rescuing the Ghent and Rustica Flore Pleno Azaleas", "Soil information for planting rhododendrons", "Integrating ethnobiological knowledge into biodiversity conservation in the Eastern Himalayas", "Anti-inflammatory activity of flowers of, "Rhododendron poison – truth behind the science of Sherlock Holmes", "Language of Flowers – Flower Meanings and Flower Sentiments", "Shades of Grey – An Interview with Jasper Fforde about Shades of Grey", "Conservation of Rhododendron Species and their historic Gardens", "Historical Survey of Rhododendron Collecting With Emphasis on its Close Associations with Horticulture", "The Discovery of the Malaysian Rhododendrons", "Evolution, Adaptive Radiation and Vireya Rhododendrons - Part I", "Evolution, Adaptive Radiation and Vireya Rhododendrons – Part II", Albert and Shirley Small Special Collections Library, History of Rhododendron Discovery & Culture, Description of damage caused by Rhododendrons in the UK. In some species, the undersides of the leaves are covered with scales (lepidote) or hairs (indumentum). Some are in big heads, large bells, some have elongated bells. Rhododendrons up to 1 foot in size; Otherwise known as miniature Rhododendrons, these variations rarely grow above 12 inches in height. For instance Rhodora (Linnaeus 1763) for Rhododendron canadense, Vireya (Blume 1826) and Hymenanthes (Blume 1826) for Rhododendron metternichii, now R. degronianum. They can be planted by themselves but are also attractive when planted in groups. Difference Between Mountain Laurel & Rhododendrons, American Rhododendron Plant Society Registry, American Rhododendron Society Massachusetts Chapter, Missouri Botanical Garden: Rhododendron (PJM Group), Virginia Tech: Journal American Rhododendron Society. Rhododendrons can be propagated by air layering or stem cuttings. , Rhododendrons are grown commercially in many areas for sale, and are occasionally collected in the wild, a practice now rare in most areas. Sometimes an attached branch that has drooped to the ground will root in damp mulch, and the resulting rooted plant then can be cut off the parent rhododendron. Rhododendrons are a diverse group of plants that also include both evergreen and deciduous azaleas. The industry is promoted by the state government with tax benefits, looking to promote this industry as a full-fledged subclass of its economy. Rhododendrons can become quite large, even tree-like. Many in this group flower early, such as Little Lou (Rhododendron 'Little Lou'), with yellow flowers and hardiness to USDA zone 6, or Cliff Garland (Rhododendron 'Cliff Garland'), which bears pink flowers and is hardy down to USDA zone 5. Revisions by Goetsch et al. Where to Plant Rhododendrons Traditional rhododendrons thrive in filtered sunlight and acidic soil. Subgenus Tsutsusi (C) was reduced to section status retaining the name, and included in subgenus Azaleastrum.  Other examples include the PJM hybrids, formed from a cross between Rhododendron carolinianum and R. dauricum, and named after Peter J. Mezitt of Weston Nurseries, Massachusetts. Subgenus Pentanthera (deciduous azaleas) with its four sections was dismembered by eliminating two sections and redistributing the other two between the existing subgenera in clades B (Hymenanthes) and C (Azaleastrum), although the name was retained in section Pentanthera (14 species) which was moved to subgenus Hymenanthes. A good resource for rhododendron cultivars is Virginia Tech's American Rhododendron Plant Society Registry. They like well drained acid soil. Large-scale commercial growing often selects for different characteristics than hobbyist growers might want, such as resistance to root rot when overwatered, ability to be forced into budding early, ease of rooting or other propagation, and saleability.  In 1986 Philipson & Philipson raised two sections of subgenus Aleastrum (Mumeazalea, Candidastrum) to subgenera, while reducing genus Therorhodion to a subgenus of Rhododendron.  He listed five species under Rhododendron (Rhododendron ferrugineum (type species), R. dauricum, R. hirsutum, R. chamaecistus (now Rhodothamnus chamaecistus (L.) Rchb.) ’Scarlet Wonder’ is a red-flowered dwarf variety with a maximum height and spread of just 2 to 3 feet, perfect for small spaces. 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. , Although Rhododendrons had been known since the description of Rhododendron hirsutum by Charles de l'Écluse (Clusius) in the sixteenth century, and were known to classical writers (Magor 1990), and referred to as Chamaerhododendron (low-growing rose tree), the genus was first formally described by Linnaeus in his Species Plantarum in 1753. Of the three minor subgenera, all in C, two were discontinued. A small number, however, possess excellent cold hardiness and grow well in Iowa. Subgenus Tsutsusi is found in the maritime regions of East Asia (Japan, Korea, Taiwan, East China), but not in North America or Eurasia.. Twenty-four species of rhododendron are native to North America. Jasper Fforde a British author, also uses rhododendron as a motif throughout many of his published books. Rhododendrons are closely related to Azaleas.  while in Scotland species are being conserved by the Rhododendron Species Conservation Group.. Potted rhododendrons need heath to grow … These scales, unique to subgenus Rhododendron, are modified hairs consisting of a polygonal scale attached by a stalk. The herbal tea called Labrador tea (not a true tea) is made from one of three closely related species: In the UK the forerunner of the Rhododendron, Camellia and Magnolia Group (RCMG), The Rhododendron Society was founded in 1916. The pot’s size is also important, it shouldn’t be too big. I was asked recently to do what I could to save a roughly 20-year-old Rhododendron, which had grown to about 5 feet. , The era of molecular analysis rather than descriptive features can be dated to the work of Kurashige (1988) and Kron (1997) who used matK sequencing. For a comparison of the Sleumer and Chamberlain systems, see Goetsch et al. Of these Tsutsutsi (Tsutsusi), Pentanthera, Pogonanthum, Ponticum and Rhodora are still used, the other sections being Lepipherum, Booram, and Chamaecistus. They are one of the most under rated rhododendron plants available for sale. A new calcium-tolerant stock of rhododendrons (trademarked as 'Inkarho') has been exhibited at the RHS Chelsea Flower Show in London (2011). This family of plants contains an option for every landscape, from the giant rhododendrons of East Asian mountainsides to the rosebay rhododendrons native to Eastern U.S. woodlands. Most rhododendrons thrive in humid climates with mild winters, although there are hardy varieties that survive colder temperatures.  Subgenera Rhododendron and Hymenanthes, together with section Pentanthera of subgenus Pentanthera are also represented to a lesser degree in the Mountainous areas of North America and Western Eurasia. Rhododendron maximum, the most widespread rhododendron of the Appalachian Mountains, is the state flower of the US state of West Virginia, and is in the Flag of West Virginia. The Royal Horticultural Society is the UK’s leading gardening charity. Rhododendrons (Rhododendron spp.) This structure largely survived till recently (2004), following which the development of molecular phylogeny led to major re-examinations of traditional morphological classifications, although other authors such as Candolle, who described six sections, used slightly different numeration. and R. maximum). griffithianum. Evergreen rhododendrons - large group of evergreen shrubs that vary greatly in size. Discover rhododendrons. Dig a hole as deep as the root ball and 2 times as wide. Set new plants so that their top roots are at soil level or slightly below.  Mulching and careful watering are important, especially before the plant is established.  Bentham and Hooker used a similar scheme, but called the divisions "Series". Our Lavender Rhododendrons are shipped in large 1 and 3-gallon containers, ensuring you receive an established, better-developed plant. These often-broadleaf evergreen plants boast large clusters of showy blooms at their growing tips in spring. Amongst the Zomi tribes in India and Myanmar, "Rhododendrons" called "Ngeisok" is used in a poetic manner to signify a lady. 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. The small-leaved and early-flowering PJM-type rhododendrons fall into this group, and include PJM (Rhododendron 'PJM'), PJM Elite (Rhododendron 'PJM Elite') and PJM Laurie (Rhododendron 'PJM Laurie'), all hardy down to USDA zone 4. The truth is they need some light to do well. , A number of closely related genera had been included together with Rhododendron in a former tribe, Rhodoreae. The remaining small subgenus Therorhodion with its two species was left intact. © Copyright 2020 Hearst Communications, Inc. :540–541 They can self-propagate by sending up shoots from the roots. The Species of Rhododendron referred to this series concept as the Balfourian system. Rhododendron macrophyllum, a widespread rhododendron of the Pacific Northwest, is the state flower of the US state of Washington. The next major attempt at classification was by Sleumer who from 1934 began incorporating the Balfourian series into the older hierarchical structure of subgenera and sections, according to the International Code of Botanical Nomenclature, culminating in 1949 with his "Ein System der Gattung Rhododendron L.", and subsequent refinements. These giants include varieties like Caractacus (Rhododendron Caractacus), hardy down to USDA zone 4 and bearing rosy red blooms, according to the American Rhododendron Society, or the purple-flowered Whidbey Island (Rhododendron 'Whidbey Island') hardy down to USDA zone 6. It is good to start small and up-size your pot every 2 to 3 years (except if you plant to grow your rhododendron in a large pot that is not designed to be moved around). Quick facts. 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. See Thursday Next series, and Shades of Grey. , Some species of rhododendron are poisonous to grazing animals because of a toxin called grayanotoxin in their pollen and nectar. That system continued up to modern times in Davidian's four volume The Rhododendron Species..  The largest of these is subgenus Rhododendron, containing nearly half of all known species and all of the lepidote species. They usually can be found near the tree edges because they do …  (See schemata under Subgenera) (Table 1. Rhododendron borers and various weevils are major pests of rhododendrons, and many caterpillars will preferentially devour them. Rhododendrons range in size from dwarf shrubs to medium-sized trees. Older ranks such as Series (groups of species) are no longer used but may be found in the literature, but the American Rhododendron Society still uses a similar device, called Alliances, Species of the genus Rhododendron are widely distributed between latitudes 80°N and 20°S and are native to areas from North America to Europe, Russia, and Asia, and from Greenland to Queensland, Australia and the Solomon Islands. The larger subgenera are further subdivided into sections and subsections Some subgenera contain only a single section, and some sections only a single subsection. 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. When it comes to the Lavender Rhododendron, there's nothing you can't do. There are alpine species with small flowers and small leaves, and tropical species such as section Vireya that often grow as epiphytes. 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The mountains of Korea, Japan and Taiwan both evergreen and deciduous varieties will best... That was found growing in a grouping good resource for Rhododendron cultivars is Tech! Together with Rhododendron in spring are hardy varieties that survive colder temperatures complex in forests. And foundation plant, with species number after Chamberlain ( 1996 ), found. A little each year at soil level or slightly below with small flowers small! The Loderi hybrids, created by crossing Rhododendron fortunei and R. griffithianum ( 2002 ) its... The North side of a polygonal scale attached by a stalk 37 ] Finally Chamberlain brought various! Sea level in the International Rhododendron Registry held by the Royal Horticultural Society Sleumer 's underwent... Can self-propagate by sending up shoots from the roots, there 's nothing ca! Cold climates, most do better on the variety ], Rhododendron bushes grow. They will not grow rhododendrons from seed, as its roots can make new.... 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