''Salix repens'', the creeping willow, is a small, shrubby species of

willow Willows, also called sallows and osiers, from the genus ''Salix'', comprise around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found primarily on moist so ...

in the family

Salicaceae The Salicaceae is the willow family of flowering plants. The traditional family (Salicaceae ''sensu stricto'') included the willows, poplar, aspen, and cottonwoods. Genetic studies summarized by the Angiosperm Phylogeny Group (APG) have greatly ...

, growing up to 1.5metres in height. Found amongst sand dunes and heathlands, it is a polymorphic species, with a wide range of variants. In the UK, at least, these range from small, prostrate, hairless plants at one end of the spectrum to taller, erect or ascending silky-leaved shrubs at the other. This wide variation in form has resulted in numerous synonyms.

Distribution

The plant has a Eurosiberian Boreo-temperate range, and is widely distributed around the coasts of western and northern Europe. In the UK, the prostrate forms (ssp. ''argentea'' and ssp. ''repens'') are characteristically found on sand dunes, growing close to the water table in

dune slack An interdunal wetland, interdunal pond or dune slack is a water-filled depression between coastal sand dunes. It may be formed either by wind erosion or by dunal encroachment on an existing wetland. The wind erosion process involves wind scooping ...

s, as well as in coastal heaths and

acid grassland Acid grassland is a nutrient-poor habitat characterised by grassy tussocks and bare ground. Habitat The vegetation is dominated by grasses and herbaceous plants, growing on soils deficient in lime (calcium). These may be found on acid sedimentary ...

, as well as being found further inland on

heath A heath () is a shrubland habitat found mainly on free-draining infertile, acidic soils and characterised by open, low-growing woody vegetation. Moorland is generally related to high-ground heaths with—especially in Great Britain—a cooler a ...

s and moorland. The erect form (var. ''fusca'') occurs in

fen A fen is a type of peat-accumulating wetland fed by mineral-rich Groundwater, ground or surface water. It is one of the main types of wetlands along with marshes, swamps, and bogs. Bogs and fens, both peat-forming ecosystems, are also known as ...

s. The species becomes more confined to moist or wet habitats in the southern and eastern parts of its UK range, and has been recorded from sea level up to (in East Perthshire).

Ecology

Dunes containing ''Salix repens'' are recognised as being of ecological importance by the

EU Habitats Directive The Habitats Directive (more formally known as Council Directive 92/43/EEC on the Conservation of natural habitats and of wild fauna and flora) is a directive adopted by the European Community in 1992 as a response to the Berne Convention. The E ...

. Over 132 Natura 2000 sites are designated for this habitat type. As the water table lowers within the slack, these Salix-dominated habitats (termed Salicion arenariae) may develop either into mesophilous (neither wet nor dry), or

xerophilous A xerophile () is an extremophilic organism that can grow and reproduce in conditions with a low availability of water, also known as water activity. Water activity (aw) is measured as the humidity above a substance relative to the humidity above p ...

(dry) communities. The former may contain species such as ''

Pyrola rotundifolia ''Pyrola rotundifolia'', the round-leaved wintergreen, is a plant species of the genus ''Pyrola ''Pyrola'' is a genus of evergreen herbaceous plants in the family Ericaceae. Under the old Cronquist system it was placed in its own family Pyr ...

'', ''

Viola canina ''Viola canina'' (heath dog-violet or heath violet) is a species of the genus ''Viola'', native to Europe, where it is found in heaths, fens, and moist woodlands, especially on acidic soils. It is a herbaceous perennial plant A perennial ...

'' and ''

Monotropa hypopitys ''Monotropa hypopitys'', the so-called Dutchman's pipe, false beech-drops, pinesap, or yellow bird's-nest, is a herbaceous perennial plant, formerly classified in the families Monotropaceae or Pyrolaceae, but now included within the subfamily Mon ...

''; the latter containing ''

Carlina vulgaris ''Carlina vulgaris'', the carline thistle, is a plant species of the genus '' Carlina''. It is a biennial that grows on limestone, chalky or other alkaline grasslands or dunes. The flowers are clusters of very small brown florets surrounded by br ...

'' and '' Thalictrum minus''. ''Salix repens'' provides shelter to other species of plant and animal. Its soft, fluffy seed hairs provide nesting material for

songbird A songbird is a bird belonging to the suborder Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 5000 ...

s, whilst in autumn there is often a rich assemblage of unusual

fungus A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from t ...

species growing in its vicinity. Should the dune slack that the plant inhabits become inundated by an advancing dune, it is able to adapt and change its growth form from erect to prostrate. Losing its erect habit, the plant is able to creep horizontally along the front of the advancing dune and survive the changing conditions. Studies have shown that

mycorrhizal A mycorrhiza (from Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the pla ...

fungal associations may assist ''Salix repens'' in expanding the ecological niches it can occupy.

Hybrids

Creeping willow may hybridise with other ''Salix'' species, typically including goat willow ('' S. caprea'') and downy willow ('' S. lapponum''). One especially rare hybrid (S. x angusensis) was discovered on Ainsdale Nature Reserve,

Lancashire Lancashire ( , ; abbreviated Lancs) is the name of a historic county, ceremonial county, and non-metropolitan county in North West England. The boundaries of these three areas differ significantly. The non-metropolitan county of Lancash ...

in 1993. It is a hybrid between three Salix species: ''S. cinerea'' ssp. ''oleifolia'' x ''S. repens'' var. ''argentea'' X ''S. viminalis''.

References

External links

* * {{Taxonbar, from=Q28141 Flora of Europe repens Plants described in 1753 Taxa named by Carl Linnaeus