Rhododendron maximum

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Rhododendron maximum
inflorescence

inflorescence

Systematics
Class : Bedecktsamer (Magnoliopsida)
Asterids
Order : Heather-like (Ericales)
Family : Heather family (Ericaceae)
Genre : Rhododendrons ( Rhododendron )
Type : Rhododendron maximum
Scientific name
Rhododendron maximum
L.

Rhododendron maximum is a species of rhododendron ( Rhododendron ) within the heather family(Ericaceae). It is distributed in eastern North America from Alabama in the south north to the coasts of Nova Scotia , where it is English great laurel, great rhododendron, rosebay rhododendron, American rhododendron, big rhododendron, Late rhododendron, Summer rhododendron, Bigleaf laurel, Deertongue laurel, Rose tree, Rose bay, Bayis, Mountain called laurel .

description

bark
Illustration from Austria's general arboriculture
Habitus
Five-fold bloom in detail

Vegetative characteristics

Rhododendron maximum grows as an evergreen shrub and reaches heights of up to 4, rarely up to 10 meters.

The alternate leaves are arranged in a petiole and a leaf blade. The leathery, coarse, simple leaf blade is oblong with a length of 10 to 19 centimeters and a width of 2 to 4 centimeters. The leaves can be poisonous. They keep their waxy, dark green surface for up to eight years, but are difficult to compost once they are dropped.

Generative characteristics

The flowering time is in June and July. The flowers are 2.5 to 3 centimeters in diameter. The corolla is white, pink, pale purple and often with greenish-yellow spots.

The dry capsule fruit is 15 to 20 millimeters long and contains numerous small seeds.

ecology

Rhododendron maximum is a clonal plant. However, it is capable of both vegetative and sexual reproduction. Vegetatively, it reproduces via subsidence and drives roots out of the aboveground parts that touch the ground.

The fruits arise from the attractive flowers between March and August. The capsule fruit ripens in autumn and soon after ripening the sides tear open, releasing a large number of tiny seeds (around 400 per capsule fruit). The microclimate requirements are relatively specific for germination (i.e., high humus content as in rotting tree trunks); otherwise the main part of reproduction takes place vegetatively through clonal growth.

As a cold-resistant species, Rhododendron reacts maximally to frost by rolling in, folding in and folding in its leaves. This protects the plants from the drying effects of cold air.
Natural range

Occurrence

Rhododendron maximum occurs in eastern North America from Nova Scotia in Canada to the eastern US states of Connecticut , Maine , Massachusetts , New Hampshire , New Jersey , New York , Ohio , Pennsylvania , Rhode Island , Vermont , West Virginia , Alabama , Georgia , Kentucky , Maryland , North Carolina , South Carolina , Tennessee and Virginia .

Rhododendron maximum is the most abundant and dominant rhododendron species in the southern Appalachians ; it occurs occasionally on fresh sites on the slopes of the Piedmont Crescent in the southeastern United States. In the north the distribution area extends to Eastern Canada (Nova Scotia).

More than 31,000 km² are inhabited by this species in the southern Appalachian Mountains, where it dominates the understory. Historically, the species' occurrence has been limited to the floodplain zones and other fresh locations, but takes advantage of disturbed areas where it spreads in drier areas. It prefers well-aerated acidic soils with a high humus content, where it produces a thick, peat-like layer. It prefers shady or partially shaded areas for optimal growth and has enormous capacities to avoid cavitation in freeze-thaw cycles. Where excessive canopy dieback has eliminated most of it, the species forms a dense and continuous secondary canopy locally referred to as laurel slicks or laurel hells . Rhododendron maximum is a significant structural and functional component of the forest ecosystem in the southern Appalachians. The status of the species remains unclear, whether it is spreading or withdrawing. In poorly drained locations on mountain ridges or upper slopes, large populations of the species have collapsed due to a Phytophthora infection or possibly also due to long periods with below-average rainfall , especially in the higher elevations . Rhododendron maximum , however, is increasingly populating areas that were previously free of evergreen undergrowth. There are still many questions unanswered to clarify the ecological role of Rhododendron maximum in the undergrowth of forests.

Systematics

The first publication of Rhododendron maximum was by Carl von Linné in Species Plantarum , 1, page 392.

Rhododendron maximum belongs to the section Ponticum from the subgenus Hymenanthes in the genus Rhododendron .

Management as an invasive plant species

The seeds of Rhododendron maximum are tiny, it is estimated that one kilogram contains about 11 million. Commercial seed production is generally from cultivated hybrids . Seeds from wild plants are generally not traded. The plants grow slowly and have great potential to sprout vegetatively. If mechanical removal is attempted as part of forestry measures, it is extremely often necessary for this species within a few years. Controlled fires have also been used against the species, but with limited success.

use

advantages

Rhododendron maximum is a striking and aesthetic component of fresh forests in the southern Appalachians. It is one of the largest and toughest rhododendron species grown commercially. Several cultivars with white to purple flowers have been grown. Where it occurs naturally, the attractive white, pink or purple flowers are produced in June, but occasionally from March to August. Rhododendron maximum keeps its dark green foliage all year round. Rhododendron maximum provides protection from low water tables and protection for wild animals. The wood is very hard and is occasionally used for special wood products.

disadvantage

Despite all its praised advantages as a naturally occurring component of the landscape or as an ornamental plant in residential and industrial areas, Rhododendron maximum can also have an inhibiting effect on the regeneration of other plant species. There is some evidence that the species has spread from the fresh locations to drier areas because of fire fighting and the lack of economic activity (e.g. grazing in mountain areas). The significance of this spread to previously unpopulated areas is concentrated around the effects of Rhododendron maximum on plant succession and the availability of resources. An occurrence of Rhododendron maximum is associated with a reduced density of saplings of wood and herbaceous plants and therefore has a strong influence on the production of wood products. The mechanism (or mechanisms) that lead to seedling reduction has been the subject of much debate. Allelopathy , competition for resources such as light, physical and chemical characteristics of forest soils and their requirements, and interactions between all these sources were discussed .

symbol

Rhododendron maximum is the state flower symbol of the US state West Virginia .

Individual evidence

  1. ↑ Rhododendron maximum . United States Department of Agriculture, Natural Resources Conservation Service. Retrieved October 21, 2015.
  2. ↑ a b Rhododendron maximum . Missouri Botanical Garden . Retrieved August 27, 2019.
  3. ↑ CS Schopmeyer: Seeds of woody plants in the United States  (= Agricultural Handbook No. 45Q). USDA Forest Service, 1974, p. 883.
  4. ↑ a b c Rhododendron maximum in the Germplasm Resources Information Network (GRIN), USDA , ARS , National Genetic Resources Program. National Germplasm Resources Laboratory, Beltsville, Maryland. Retrieved August 29, 2019.
  5. ^ RE Swanson: A Field Guide to the Trees and Shrubs of the Southern Appalachians . The Johns Hopkins University Press, Baltimore, MD 1994, p. 399.
  6. ^ MM Dobbs: Spatial and temporal distribution of the evergreen understory in the southern Appalachians . University of Georgia, Athens, GA 1995, p. 100: “M. Sci. Thesis "
  7. ↑ CC Lipp, ET Nilsen: The impact of subcanopy light environment on the hydraulic vulnerability of Rhododendron maximum to freeze-thaw cycles and drought . In: Plant, Cell and Environment . 20, 1997, pp. 1.264-1.272.
  8. ^ BD Clinton, JM Vose: Plant succession and community restoration following felling and burning in the southern Appalachian Mountains . In: WK Moser & CF Moser (eds.): Fire and forest ecology: innovative silviculture and vegetation management  (= Tall Timbers Fire Ecology Conference Proceedings), Volume 21. Tall Timbers Research Station, Tallahassee, FL 2000, pp. 22-29 .
  9. ^ CL Brown, LK Kirkman: Trees of Georgia and Adjacent States . Timber Press, Portland, OR 1990, p. 292.
  10. ^ MM Dobbs: Dynamics of the evergreen understory at Coweeta . University of Georgia, Athens GA 1998, p. 179: "PhD Dissertation"
  11. ^ BD Clinton, JM Vose: Effects of Rhododendron maximum L. on Acer rubrum L. seedling establishment . In: Castanea . 61, No. 1, 1996, pp. 38-45.
  12. ↑ a b E. T. Nilsen, BD Clinton, TT Lei, K. Miller, SW Semones, JF Walker: Does Rhododendron maximum L. (Ericaceae) reduce the availability of resources above and belowground for canopy tree seedlings? . In: American Midland Naturalist . 145, 2001, pp. 325-343.
  13. ↑ ET Nilsen, JF Walker, OK Miller, SW Semones, TT Lei, BD Clinton: Inhibition of seedling survival under Rhododendron maximum (Ericaceae): could allelopathy be a cause? . In: American Journal of Botany . 86, No. 11, 1999, pp. 1.597-1.605 ..

Web links

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