Dryas octopetala
Mountain Avens ( Dryas octopetala )
The White Mountain Avens ( Dryas octopetala ) belongs to the genus Dryas in the rose family ( Rosaceae ). The mountain avens is a symbol of the Alps and probably the most distinctive type of a trellis shrub.
Origin of the name
The genus was named in the 16th century Chamaedrys what dwarf oak (from Greek Chamei = dwarf and drys oak) means. Carolus Linnaeus gave the genus in the 18th century the name Dryas with the botanical addition octopetala due to the mostly eight white petals. This is an exception in the family, in the otherwise fivefold flowers are common.
Description of the plant
The evergreen shrub trellis reaches stature heights between five and 15 centimeters and can live up to 100 years old. He has prostrate, woody shoots that can cover large areas. The creeping stems and branches can here reach a length of up to one meter.
The short- stalked leaves have notched a rolled- edge and the top is bare, but the bottom shining through a fine, weißfilzige hair, which derives its name. This hair is used as transpiration for the inwardly displaced stomata. The leaves are alternate arranged, however, frequently arranged in rosettes. They are up to three inches long and an inch wide around. The stipules are widely adherent to the petiole.
The hermaphrodite, radial symmetry flowers have a diameter of 2-4 centimeters and grow singly from the leaf axils. The eight pure white or creamy white petals are outside braunfilzig. The flowering period lasts from June to August.
The stylus is prolonged in the maturity of the fruit and is used with his hairy projections for wind dispersal of the fruit. Fruit ripening occurs from July.
Occurrence
The species is arctic - alpine widespread. The area includes not only the Alps and other mountain ranges of central and southern Europe, the Arctic region, Northern Europe, Siberia, East Asia and North America. In northern Sweden, the avens, together with mosses and lichens, the main vegetation of the tundra. In the south the range of the species extends to northern Spain, central Italy and southern Bulgaria.
As location dwarf shrub heath arctic tundra, moraine, rock corridors, mats and Kalkschuttflure be above the treeline preferred. In the Alps, this species is found 1200-2500 meters. In northern Europe, more acidic soils are preferred.
Dryas octopetala and more often their hybrids with the North American species Dryas drummondii Dryas × suendermannii find occasional use as ornamental plants in rock gardens.
During the Younger Dryas (about 10730-9700 BC), the species was spread everywhere in Europe, as is evident from the pollen analyzes from this period. The period at the end of the Pleistocene was named after this plant.
Ecology
The plant is extremely frugal, if she gets enough light. Since the plant only a few weeks a year is metabolically active, it can reach a ripe old age of up to 100 years.
The flowers are tracked during the short arctic or alpine summer as a parabolic antenna of the sun. As heat collector they thus represent an attractive landing place for insects represents the shoot and flower buds are already created in the previous growing season.
The White Mountain Avens has root nodules that bind atmospheric nitrogen with actinomycetes of the genus Frankia. They also enter into a symbiosis with Ektomykorrhizapilzen, such as the strong -smelling Chanterelle, Tomentella sp., Dryadirhiza fulgens and C. geophilum.
System
Depending on the view, the genus includes two to three species ( Dryas drummondii Dryas Dryas integrifolia and octopetala ).
The pale yellow-flowered species D. drummondii and the white-flowered D. integrifolia inhabit the mountains of North America, where D. integrifolia is also regarded as a variety of D. octopetala (D. octopetala var integrifolia ).
Others
The White Mountain Avens is often obtained excellent fossil. The flowers, fruits and pollen have survived in glacial clay deposits thousand years. The plant was with decay of the ice age spread all over Germany ( proof of pollen analysis). After this plant this time was called Dryas time ( Avens time).
This species is regional basis protected by law. The mountain avens is the symbolic plant of the Swedish province of Lapland and Iceland's national flower since 2004.