Leaves are sclerophyllous, simple, alternate, and oblong (10 to 30 cm long, 5 to 8 cm wide). Some of the fastest growing rhododendrons are the Brittenhill Bugle, R. genestierianum, Ilam Cream, Mother of Pearl, Professor Hugo de Vries, Spicy Nutmeg, and the Whidbey Island. By creating an account you agree to the Hunker, American Rhododendron Society: Alphabetized Plant List, National Gardening Association: Plant Care Guides -- Rhododendron. It produces large, showy, white to purple flowers each June and July.. These plants generally grow about 3 inches per year, reaching their maximum height of up to 36 inches in 10 years. The fastest-growing rhododendron cultivars grow 7 feet in 10 years, according to the American Rhododendron Society's website. Central and southern Appalachian montane oak forest, 10.2305/IUCN.UK.2018-2.RLTS.T82889952A135956342.en, 10.1674/0003-0031(2001)145[0325:DRMLER]2.0.CO;2, https://en.wikipedia.org/w/index.php?title=Rhododendron_maximum&oldid=982281373, Creative Commons Attribution-ShareAlike License, This page was last edited on 7 October 2020, at 06:02. This species affords protection to steep watersheds and shelter for wildlife. It prefers deep well-drained acid soils high in organic matter where it produces a thick, peat-like humus. It grows 10-20 feet… 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. The fruit is a dry capsule 15–20 mm (.60-.79 in) long, containing numerous small seeds. Rosebay rhododendron is an important structural and functional component of southern Appalachian forest ecosystems. Germination rates range from 75% to 90% . The mechanism(s) by which rosebay rhododendron reduces seedling survival has been the subject of much debate. As long as the area receives shade after 11:00 AM or so, the plants will grow well. It is capable, however, of reproducing both vegetatively and sexually. Description. Prescribed fire has also been used to control this species but with limited success.. Rosebay Rhododendron performs poorly in exposed sunny positions, though a spot with morning sun is fine. In: Argent, George; McFarlane, Marjory, eds. Rhododendrons have no ultimate size, they can carry on growing indefinitely. The leaves are 9–19 cm (3–8 in) long and 2–4 cm (0.75-1.5 in) broad. Rhododendrons (Rhododendron spp.) Moisture and length of growing season greatly affect rate of growth: mild wet areas may have twice the growth rate of cold dry ones. Rhododendrons in horticulture and science: International Rhododendron conference: Proceedings; 2002; Edinburgh, UK. The leaves can be poisonous. Rosebay rhododendron is a striking and aesthetically pleasing feature of mesic southern Appalachian forests. Rhododendron maximum is an evergreen shrub growing to 4 m (13 ft), rarely 10 m (33 ft), tall. The cultivars all vary by their time of blooming, bloom color and USDA hardiness zones. The flowers are 2.5–3 cm (1 in) diameter, white, pink or pale purple, often with small greenish-yellow spots. 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. The fastest-growing rhododendron cultivars grow 7 feet in 10 years, according to the American Rhododendron Society's website. Growth rate: Moderate Average landscape size: Moderate growing; reaches 6 to 8 ft. tall, 8 to 10 ft. wide. What isn’t clear is whether or not we are in a period of advancement or retreat for this species.  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. The flowers are 2.5–3 cm (1 in) diameter, white, pink or pale purple, often with small greenish-yellow spots. Range of Growing Rate The society's website lists 44 named cultivars that grow 1 foot in 10 years, 164 cultivars that grow 2 feet, 366 cultivars that grow 3 feet, 281 cultivars that grow 4 feet, 288 cultivars that grow 5 feet and 186 cultivars that grow 6 feet in 10 years. Rhododendrons grow from 1 to more than 20 feet tall, depending on the species, according to a National Gardening Association website article. Seeds from wild sources are not commonly sold commercially. It reproduces vegetatively through a process called ‘layering’ where it produces roots from above ground woody parts when in contact with the forest floor. Slow growth rate: Rhododendron maximum: 15' to 20' Partial shade: N.A. are flowering shrubs that are hardy in U.S. Department of Agriculture plant hardiness zones 4 through 9, depending on the variety. The leaves are 9–19 cm (3–8 in) long and 2–4 cm (0.75-1.5 in) broad. Slower growing rhododendrons tend to be smaller cultivars while the fastest growers take up more space. Yet, rosebay rhododendron now occupies sites that historically were free of evergreen understory. Rhododendron maximum, commonly called rosebay rhododendron or great laurel, is a large, upright, loose, multi-stemmed, late-blooming, evergreen shrub that is native to North America from Ontario and Nova Scotia south to Ohio, Alabama and Georgia with a concentration of plants in the southern Appalachian Mountains where it typically grows in dense thickets which dominate the understory in some locations. Rhododendron maximum is an evergreen shrub growing to 4 m (13 ft), rarely 10 m (33 ft), tall. Approximately 12,000 square miles in the southern Appalachians are occupied by this species where it dominates the understory. A one-time farm boy, Richard Hoyt, holder of a PhD in American studies, is a former newspaper reporter, magazine writer and college professor. It is one of the largest and hardiest rhododendrons grown commercially. Edinburgh, UK: Royal Botanic Garden Edinburgh: 259 … 'Wilson' Rhododendron-One of the best broadleaf evergreens for foliage.-Useful in mass plantings and grouping-Excellent as a neutral filler at the base of leggy plants for borders  Where it occurs naturally, it produces a showy, white, pink, or light purple flower primarily in June, but occurs from March into August. Many rhododendron plants grow from 3 to 4 feet in 10 years, but some can grow up to 7 feet in 10 years. The fruit is produced from showy flowers from March to August. Leaves are sclerophyllous, simple, alternate, and oblong (10 to 30 cm long, 5 to 8 cm wide). While writing 27 novels of suspense, he has lived on sugar cane, pepper and papaya plantations and helped keep bees in Belize. Rhododendron maximum is one of two elepidote species native to eastern North America and widely found in the Southeastern Appalachian Mountains.  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 leaves are 9–19 cm (3–8 in) long and 2–4 cm (0.75-1.5 in) broad. 'Compact Maximum' is thought to have originated as a seedling of the hybrid Rhododendron 'Maximum Roseum', a pink flowering form of the native species. Hunker may earn compensation through affiliate links in this story. 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.  The significance of this movement onto previously unoccupied sites centers around the impacts of rosebay rhododendron on plant succession and resource availability.