Eared willow is a large, multi-branched woody shrub and a pioneer species, commonly occurring in wet sites in the Caledonian Forest.
Eared willow is native to Europe, and is distributed over much of the continent, from Scandinavia to Spain, and from the UK to Russia. It is most common in central and northern regions, but is also found in Albania, Bulgaria and the island of Corsica, although it is absent from Italy and Greece. It has been introduced to the state of Pennsylvania in the USA.
Distribution in Scotland
Eared willow occurs throughout Scotland, including the Western Isles and Orkney, and it is one of the few trees that grow as far north as North Voe on the mainland of Shetland. Because it prefers moist sites and slightly acid soils, it is more common in the north and west of the country and occurs especially in damp woods, heaths and moors. It also forms part of the montane scrub community at the treeline, and has been recorded at elevations of up to 780 metres in the UK.
Eared willow is a member of the willow family, Salicaceae, in which it is grouped with the sallows - in fact an alternative name sometimes used for the species is eared sallow. It is considered to be a shrub, rather than a tree, and it can reach 3 metres in height with stems up to 20 cm. in diameter. It is typically rounded and bushy in shape, with multiple stems spreading out at, or near, ground level. The bark is grey and smooth, although in older individuals there can be large cracks or splits running longitudinally on the stems. Twigs are a dark reddish-brown in colour, and the scales which cover the buds are yellow-brown and darker at their tips.
Eared willow is deciduous, so it is leafless in winter, with the new leaves appearing in April or early May. The leaves are grey-green in colour, and are wrinkled, or rugose, in texture. They are slightly hairy, or pubescent, especially on the underside. The shape of the leaves is elliptic or lanceolate, meaning lance-like, and the widest point is closer to the tip than the base of the leaf. The leaves measure up to 4 or occasionally 6 cm in length and 3 or sometimes 4 cm in width. The most distinctive feature is the 'ears' or stipules which give the species its common name. These are small leafy appendages that are somewhat ear-like in shape, and grow on each side of the leaf stem, near the base of, but separate from, the leaf itself. The leaves turn yellow in October before being shed for the winter.
Like the other members of the genus Salix, eared willow is dioecious, meaning that individual trees are either male or female (in contrast to most trees, such as Scots pine, for example, where male and female flowers occur on the same tree). The flowers appear just before the leaves open in spring, with the male flowers or catkins, which are about 1.5 cm. long, opening to reveal numerous white stamens tipped with yellow pollen. The female flowers are more upright and develop thicker pale green carpels which receive the pollen. Pollination is carried out by insects, mainly by bees, but also by hoverflies. Pollinated female flowers produce tiny seeds that ripen in May or June, and are dispersed by the wind, aided by white cottony tufts attached to them. Eared willow also propagates easily from branch cuttings that are inserted directly into the ground.
Eared willow is a pioneer species, meaning that it readily colonises open ground, and it can often be the first woody species to get established on wetter areas. It can grow rapidly, branching profusely to produce its characteristic spreading bushy shape. Like other willows, it readily hybridises, particularly with grey willow (Salix cinerea), tea-leaved willow (Salix phylicifolia) and creeping willow (Salix repens), and this can make identification of the species problematical at times.
Ecological relationships of eared willow
Although it is not as large or conspicuous as the trees in the forest, eared willow is nonetheless a significant part of the ecosystem, especially where the ground is damp or wet, and a range of other organisms are associated with it. Underground, eared willow forms ectomycorrhizal relationships with fungi, in which the roots of the fungi surround the plant's roots without penetrating them, and a mutually beneficial exchange of nutrients takes place. Other fungi are more visible and less beneficial, and eared willow is susceptible to infection by a rust fungus (Melampsora capraearum) which appears as spots on the leaves.
The stems and branches provide the habitat for a number of mosses and lichens, and on the lower sections mosses such as common tamarisc-moss (Thuidium tamariscinum), and cypress-leaved plait-moss (Hypnum cupressiforme) can be found. Higher up, generally only pincushion mosses, such as crisped pincushion (Ulota crispa) and Bruch's pincushion (Ulota bruchii) occur. Lichens which occur on eared willow include widely-distributed and abundant species such as Platismatia glauca and puffed shield lichen (Hypogymnia physodes), while a rare species (Pseudocyphellaria crocata) has been found on it at Balmacara in Lochalsh.
The Salix genus as a whole in the UK supports 450 species of invertebrates, so unsurprisingly, eared willow has a range of insects which feed on it. The caterpillars of a number of moths feed on eared willow, and two which are particularly associated with it in Scotland are the ruddy highflyer (Hydriomena ruberata) and a tortrix moth (Epinotia subocellana). The larvae of cousin German (Protolampra sobrina), a rare moth that is the subject of a UK Biodiversity Action Plan, have recently been discovered feeding on eared willow in Speyside. The larvae of a sawfly (Nematus miliaris) also feed on the leaves.
A rare species in Britain that is particularly associated with eared willow is the 10 spotted pot beetle (Cryptocephalus decemmaculatus). The adult beetles feed on the leaves, and the larvae feed on fallen leaves. This beetle is a Priority Species in the UK's Biodiversity Action Plan, and is only known to occur at Rannoch and Braemar in the Highlands, and at some sites in Staffordshire and Cheshire in England.
Galls are induced on the leaves of eared willow by various invertebrates. These include pustules on the upper surface, caused by a mite (Aculus laevis), and harder galls caused by two midges (Iteomyia capreae and I. major). Another midge (Rabdophaga cinerearum) induces the formation of a tiny rosette of leaves at the tip of the twig. Elsewhere in Europe, a sawfly (Euura auritae) causes the formation of spindle-shaped galls on the stems.
Eared willow is an important food plant in winter for the European beaver (Castor fiber), which was hunted to extinction in Scotland by the 16th century. Because of its preference for growing in wet sites and its ability to naturally coppice (ie to send out new stems from the base of one that is damaged), eared willow is well-suited to thrive in the presence of beavers.
Together with some of its close relatives, such as grey willow (Salix cinerea) and goat willow (Salix caprea), it also forms part of willow carr (wet woodland dominated by willows), which is an important habitat for invertebrates.
Alan Watson Featherstone