The Purple Willow is a pioneer shrub colonizing recently-formed gravel islands and river banks in the wetlands of the Alpine foothills. Characteristic are its thin, flexible stems which often display a reddish hue; these excellent materials are often harvested for binding. The shrub's intensive root structure makes it possible for it to penetrate deep into gravel and to fortify these locations.
Description
The Purple Willow is generally a medium-sized shrub reaching a maximum height of 6m with an upright oval habit which may sometimes appear tree-like in form. Common characteristics: the relatively upright posture of the twigs (especially of young shrubs) and the large number of stump suckers. The Purple Willow has a well-developed, extensive root system which enables it to penetrate deep into gaps between the layers of gravel and to provide a firm grip for the shrub. The long young shoots are glossy; on the side of light, dark red to reddish brown, and on the shaded side yellowish-brown. The buds are hairless, dark red and glossy, most often skewed opposite and sometimes alternate. The species is easily identifiable as the only willow type with a (primarily) opposite leaf arrangement. Although leaf size may vary considerably, the shape is usually consistent: narrow, lanceolate, broadest in the front part of the leaf and gradually merging towards the leaf base; slightly pointed at the front and finely-toothed from the middle to the tip. Upper side is blue-green to dull green while the underside greyish-green. There are no stipules and pilosity occurs only during foliation. A dioecious species, the Purple Willow flowerheads appear prior to foliation which, depending on the location, may take place between the months March and May. The male catkins are opposite, upright, around 5cm long and 1cm wide with long, hairy blackish-brown bracts; there are coadunate filaments along the entire length. The upright yet slightly bent female catkins are approx. 6cm long, around 6-10mm wide with downy-haired ovaries sitting parallel to the stem, very short or even absent styles, and stigma building conspicuous heads. The fruit consists of small, very densely-gathered bifid capsules; when ripe, both carpels open up in the shape of a sickle from the top down.
Distribution
The Purple Willow inhabits a huge area encompassing most parts of Eurasia: east from Great Britain to the Baltic coast and extending all the way through Central Asia and China. The southern European border is formed by a narrow coastal area in northern Africa. In Valais (Switzerland) it has been documented at elevations as high as 2300m, yet prefers sub-Alpine and colline elevations. In Austria, it is one of the most common willow shrubs and may be found in all provinces. In the Donau-Auen National Park, it may often be sighted on gravel substrates along the Danube and somewhat less often farther away from the river.
Endangerment and Conservation Status
Not vulnerable in Austria or Europe.
Ecological Characteristics
The Purple Willow is frost and drought-resistant and overall a very hardy pioneer plant able to locate its ideal soils: moist and/or seasonally-flooded, alluvial, calcareous. It is especially common on the banks of creeks and rivers as well as on gravel and sandbars of rivers just to the north of the Alps. In the settlement pattern of gravel areas, there is in fact a phase named after the species – the "Purple Willow Bush". As "sediment catcher" the Purple Willow primes the location for the settlement of the White Willow.
Special Characteristics
Since time immemorial, the manifold uses of the Purple Willow have made it one of the most commonly utilized shrubs. As a material for binding, braiding and basket-making, its thin, flexible twigs are used for example by winemakers to tie vines. Thanks to its robust root system, the species is often planted on embankments for erosion control and to "green up" wild streams.