Salix cinerea is a species of willow

Willow

Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere...

 native to Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 and western Asia

Asia

Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

.

It is a deciduous

Deciduous

Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...

 shrub

Shrub

A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...

 or small tree

Tree

A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

 growing to 4-15 m high. The leaves

Leaf

A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 are spirally arranged, 2–9 cm long and 1–3 cm broad (exceptionally up to 16 cm long and 5 cm broad), green above, hairy below, with a crenate margin. The flower

Flower

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

s are produced in early spring in catkin

Catkin

A catkin or ament is a slim, cylindrical flower cluster, with inconspicuous or no petals, usually wind-pollinated but sometimes insect pollinated . They contain many, usually unisexual flowers, arranged closely along a central stem which is often drooping...

s 2–5 cm long; it is dioecious

Plant sexuality

Plant sexuality covers the wide variety of sexual reproduction systems found across the plant kingdom. This article describes morphological aspects of sexual reproduction of plants....

 with male and female catkins on separate plants. The male catkins are silvery at first, turning yellow when the pollen is released; the female catkins are greenish-grey, maturing in early summer to release the numerous tiny seed

Seed

A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s embedded in white cottony down which assists wind dispersal.

There are two subspecies

Subspecies

Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

:

• Salix cinerea subsp. cinerea. Central and eastern Europe, western Asia. Shrub to 4–6 m (rarely 10 m) tall, with smooth bark. Leaves densely hairy below with pale yellow-grey hairs; stipules large, persistent until autumn.
• Salix cinerea subsp. oleifolia (Sm.) Macreight (syn. S. atrocinerea Brot.). Western Europe, northwest Africa. Shrub or tree to 10–15 m tall, with furrowed bark. Leaves thinly hairy below with dark red-brown hairs; stipules small, early deciduous.

There is some overlap in the distributions (not indicated in the map, right), with both occurring in a broad band north to south through France, and scattered specimens of subsp. cinerea west to Ireland, western France, and Morocco; scattered specimens of subsp. oleifolia occur east to the Netherlands. Specimens of subsp. oleifolia in southern Scandinavia are planted or naturalised, not native. Intermediate specimens also occur.

Ecology

It usually grows in wetland

Wetland

A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....

s. The two subspecies differ slightly in requirements, with subsp. cinerea generally restricted to basic marshland and fen habitats, while subsp. oleifolia is less demanding, occurring in both basic marshes and acidic bogs and streamsides.a
la lala

Invasive species

S. cinerea is an invasive species

Invasive species

"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

 in New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

 and is listed on the National Pest Plant Accord

National Pest Plant Accord

The National Pest Plant Accord identifies pest plants that are prohibited from sale and commercial propagation and distribution across New Zealand....

which means that it cannot be sold or distributed.