Rhododendron maximum

Life-forms

Classification System: APG IV

Superregnum: Eukaryota
Regnum: Plantae
Cladus: Angiosperms
Cladus: Eudicots
Cladus: Core eudicots
Cladus: Asterids
Ordo: Ericales

Familia: Ericaceae
Subfamilia: Ericoideae
Tribus: Rhodoreae
Genus: Rhododendron
Subgenus: R. subg. Hymenanthes
Sectio: R. sect. Pontica
Subsectio: R. subsect. Pontica
Species: Rhododendron maximum
Name

Rhododendron maximum L., 1753.
Synonyms

Hymenanthes maxima (L.) H.F.Copeland
Rhododendron ashleyi Coker
Rhododendron bigener hort. ex Steud.
Rhododendron fragrans hort. ex DC.
Rhododendron maximum f. apetalum V.V.Byalt & Firsov
Rhododendron maximum var. leachii B.E.Harkn. ex D.H.Voss
Rhododendron procerum Salisb.
Rhododendron purpureum G.Don
Rhododendron purshii G.Don
Rhododendron tigrinum hort. ex Steud.

Hybrids

R. × cunninghamii – R. × halopeanum – R. × hybridum – R. × intermedium – R. × norbitoense – R. × pictum – R. × standishii – R. × superponticum – R. × wellesleyanum
Homonyms

Rhododendron maximum Thunb. (1784) = Rhododendron scabrum G.Don
Rhododendron maximum Hook. (1837) = Rhododendron macrophyllum D.Don ex G.Don.

Distribution
Native distribution areas:
Rhododendron maximum

Continental: Northern America
USA (Alabama, Connecticut, District of Columbia, Delaware, Georgia, Kentucky, Massachusetts, Maryland, Maine, North Carolina, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia, Vermont, West Virginia), Canada (Nova Scotia)

References: Brummitt, R.K. 2001. TDWG – World Geographical Scheme for Recording Plant Distributions, 2nd Edition
References
Primary references

Linnaeus, C. 1753. Species plantarum, exhibentes plantas rite cognitas, ad genera relatas, cum differentiis specificis, nominibus trivialibus, synonymis selectis, locis natalibus, secundum systema sexuale digestas. Tomus I. Pp. [I–XII], 1–560. Impensis Laurentii Salvii, Holmiae [Stockholm]. BHL Reference page. : 392.

Links

Hassler, M. 2020. Rhododendron maximum. World Plants: Synonymic Checklists of the Vascular Plants of the World In: Roskovh, Y., Abucay, L., Orrell, T., Nicolson, D., Bailly, N., Kirk, P., Bourgoin, T., DeWalt, R.E., Decock, W., De Wever, A., Nieukerken, E. van, Zarucchi, J. & Penev, L., eds. 2020. Species 2000 & ITIS Catalogue of Life. Published online. Accessed: 2020 May 14. Reference page.
Govaerts, R. et al. 2020. Rhododendron maximum in Kew Science Plants of the World Online. The Board of Trustees of the Royal Botanic Gardens, Kew. Published online. Accessed: 2020 May 14. Reference page.
International Plant Names Index. 2020. Rhododendron maximum. Published online. Accessed: May 14 2020. Reference page.
Tropicos.org 2020. Rhododendron maximum. Missouri Botanical Garden. Published online. Accessed: 14 May 2020.
USDA, ARS, Germplasm Resources Information Network. Rhododendron maximum in the Germplasm Resources Information Network (GRIN), U.S. Department of Agriculture Agricultural Research Service.

Vernacular names
English: great laurel, great rhododendron, rosebay rhododendron, American rhododendron
polski: Różanecznik olbrzymi
русский: Рододендрон крупнейший

Rhododendron maximum is a species of Rhododendron native to the Appalachians of eastern North America, from Alabama north to coastal Nova Scotia. Its common names include great laurel,[2] great rhododendron, rosebay rhododendron, American rhododendron and big rhododendron.
Description

Rhododendron maximum is an evergreen shrub growing to 4 m (13 ft), rarely 10 m (33 ft), tall. The leaves are 9–19 cm (3.5–7.5 in) long and 2–4 cm (0.79–1.57 in) broad.[3] The flowers are 2.5–3 cm (0.98–1.18 in) diameter, white, pink or pale purple, often with small greenish-yellow spots. The fruit is a dry capsule 15–20 mm (0.59–0.79 in) long, containing numerous small seeds. The leaves can be poisonous. Leaves are sclerophyllous, simple, alternate, and oblong (10 to 30 cm long, 5 to 8 cm wide). It retains its waxy, deep-green leaves for up to 8 years, but once shed are slow to decompose. It produces large, showy, white to purple flowers each June and July.[3]
Bark of Rhododendron maximum
Distribution and habitat

Rosebay rhododendron is the most frequently occurring and dominant species of Rhododendron in the southern Appalachian region,[4] and occurs occasionally on mesic hill-slopes throughout the upper Piedmont Crescent of the Southeastern United States.
Ecology
American rhododendron (Rhododendron maximum)

Approximately 12,000 square miles in the southern Appalachians are occupied by this species[5] where it dominates the understory. This species has historically been confined to riparian areas and other mesic sites but takes advantage of disturbed areas where it is present to advance onto sub-mesic sites. It prefers deep well-drained acid soils high in organic matter where it produces a thick, peat-like humus. It prefers low to medium light conditions for optimum carbon gain, and has a tremendous capacity for avoiding cavitation during freeze-thaw cycles.[6] Where extensive overstory mortality has eliminated most of the overstory, this species forms a thick and continuous subcanopy known locally as 'laurel slicks' or 'laurel hells'. Rosebay rhododendron is an important structural and functional component of southern Appalachian forest ecosystems. What is not clear is whether or not we are in a period of advancement or retreat for this species. For example, on poorly drained sites on ridge or upper slope positions, large areas of rosebay rhododendron, particularly at the high elevations, have recently died out presumably due to the Phytophthora fungus, or due to recent prolonged periods of below-average precipitation. Yet, rosebay rhododendron now occupies sites that historically were free of evergreen understory. There are still important questions to be answered regarding this species to completely understand its role in forest understories.

In North Carolina, US, Pestalotiopsis which is a genus of ascomycete fungi causes grey-brown spots on the living leaves.[7]
Reproduction

Rosebay rhododendron is clonal. It is capable, however, of reproducing both vegetatively and sexually. It reproduces vegetatively through a process called 'layering' where it produces roots from above ground woody parts when in contact with the forest floor. The fruit is produced from showy flowers from March to August. The fruit is an oblong capsule that ripens in the fall, and splits along the sides soon after ripening to release large numbers of minute seed (c. 400 per capsule).[8] Microsite requirements for seed germination are relatively specific (e.g., high in organic matter such as rotting logs); hence, the majority of reproduction is vegetative resulting in a clonal distribution.
A cold-hardy species, R. maximum responds to subfreezing temperatures by curling, folding down, and clamping shut its foliage. This action helps protect the shrub from the desiccating effects of cold air.
Cultivation

Seeds from rosebay rhododendron are minute and it is estimated that approximately 11 million are contained in 1 kg. Commercial seed production is generally from cultivated hybrids. Seeds from wild sources are not commonly sold commercially. Rosebay rhododendron is a slow-growing shrub and has a very high sprout potential. If mechanical removal is attempted in the case of forest management, extremely high densities are attained by this species in a matter of a few years. Prescribed fire has also been used to control this species but with limited success.[9]
Uses

Rosebay rhododendron is a striking and aesthetically pleasing feature of mesic southern Appalachian forests. It is one of the largest and hardiest rhododendrons grown commercially. Several cultivars with white to purple flowers have been selected for the horticultural trade.[10] Where it occurs naturally, it produces a showy, white, pink, or light purple flower primarily in June, but occurs from March into August. Rosebay rhododendron maintains deep-green foliage year round. This species affords protection to steep watersheds and shelter for wildlife. The wood is very hard and is occasionally used for specialty wood products.
Detrimental effects

For all its prized qualities as a naturally occurring component of the landscape or as plantings in residential and commercial landscaping, rosebay rhododendron can have an inhibitory effect on regeneration of other plant species. There is some evidence to suggest that due to fire suppression and the absence of other cultural activities (i.e., mountain-land grazing), this species has advanced beyond the mesic forest sites into sub-mesic understories.[11] The significance of this movement onto previously unoccupied sites centers around the impacts of rosebay rhododendron on plant succession[12] and resource availability.[13] Rosebay rhododendron is associated with reduced woody and herbaceous seedling abundance throughout its range, and hence poses a serious impediment to the production of wood products. The mechanism(s) by which rosebay rhododendron reduces seedling survival has been the subject of much debate. Possible sources of inhibition include allelopathy, competition for resources including light, physical and chemical attributes of the forest floor and soil, and interactions between some or all sources.[14][13]
Alternate common names

R. maximum has also been called:

Great rhododendron
Late rhododendron
Summer rhododendron
Great laurel
Bigleaf laurel
Deertongue laurel
Rose tree
Rose bay
Bayis

Symbolism

Rhododendron maximum is the state flower of the U.S. state of West Virginia.[15]
See also

Catawbiense hybrid – R. catawbiense and R. maximum hybrids
Central and southern Appalachian montane oak forest
List of Rhododendron species

References

Botanic Gardens Conservation International (BGCI).; IUCN SSC Global Tree Specialist Group (2018). "Rhododendron maximum". IUCN Red List of Threatened Species. 2018: e.T82889952A135956342. doi:10.2305/IUCN.UK.2018-2.RLTS.T82889952A135956342.en. Retrieved 19 November 2021.
NRCS. "Rhododendron maximum". PLANTS Database. United States Department of Agriculture (USDA). Retrieved 21 October 2015.
"Rhododendron maximum". Missouri Botanical Garden. Retrieved 2019-08-27.
Swanson, R. E. (1994). A Field Guide to the Trees and Shrubs of the Southern Appalachians. Baltimore, MD: The Johns Hopkins University Press. p. 399.
Dobbs, M. M. (1995). Spatial and temporal distribution of the evergreen understory in the southern Appalachians (M. Sci. Thesis). Athens, GA: University of Georgia. p. 100.
Lipp, C. C.; Nilsen, E. T. (1997). "The impact of subcanopy light environment on the hydraulic vulnerability of Rhododendron maximum to freeze-thaw cycles and drought". Plant, Cell and Environment. 20 (10): 1.264 – 1.272. doi:10.1046/j.1365-3040.1997.d01-22.x.
Maharachchikumbura, S.S.N.; Hyde, K.D.; Groenewald, J.Z.; Xu, J.; Crous, P.W. (September 2014). "Pestalotiopsis revisited". Studies in Mycology. 79: 121–186. doi:10.1016/j.simyco.2014.09.005. PMC 4255583. PMID 25492988.
Schopmeyer, C. S. (1974). Seeds of woody plants in the United States. Agricultural Handbook No. 45Q. USDA Forest Service. p. 883.
Clinton, B. D.; Vose, J. M. (2000). "Plant succession and community restoration following felling and burning in the southern Appalachian Mountains". In W. K. Moser & C. F. Moser (ed.). Fire and forest ecology: innovative silviculture and vegetation management. Tall Timbers Fire Ecology Conference Proceedings. Vol. 21. Tallahassee, FL: Tall Timbers Research Station. pp. 22–29.
Brown, C. L.; Kirkman, L. K. (1990). Trees of Georgia and Adjacent States. Portland, OR: Timber Press. p. 292.
Dobbs, M. M. (1998). Written at Athens GA. Dynamics of the evergreen understory at Coweeta (PhD Dissertation). Hydrologic Laboratory, North Carolina: University of Georgia. p. 179.
Clinton, B. D.; Vose, J. M. (1996). "Effects of Rhododendron maximum L. on Acer rubrum L. seedling establishment". Castanea. 61 (1): 38–45.
Nilsen, E. T.; Clinton, B. D.; Lei, T. T.; Miller, K.; Semones, S. W.; Walker, J. F. (2001). "Does Rhododendron maximum L. (Ericaceae) reduce the availability of resources above and belowground for canopy tree seedlings?". American Midland Naturalist. 145 (2): 325–343. doi:10.1674/0003-0031(2001)145[0325:DRMLER]2.0.CO;2. S2CID 7021773.
Nilsen, E. T.; Walker, J. F.; Miller, O. K.; Semones, S. W.; Lei, T. T.; Clinton, B. D. (1999). "Inhibition of seedling survival under Rhododendron maximum (Ericaceae): could allelopathy be a cause?". American Journal of Botany. 86 (11): 1.597 – 1.605. doi:10.2307/2656796. JSTOR 2656796.

Fenn, Christine D. (24 January 2018). "Rhododendron". e-WV: The West Virginia Encyclopedia. Retrieved 22 April 2024.

"Rhododendron maximum". Germplasm Resources Information Network. Agricultural Research Service, United States Department of Agriculture.

External links

USDA Plants Profile of Rhododendron maximum (great rhododendron)
Interactive Distribution Map for Rhododendron maximum
Plants for a Future: Rhododendron maximum
Vanderbilt.edu Bioimages: Rhododendron maximum