Grzegorz Lesniewski / Riparian forest with Crack Willow (Salix fragilis), White Willow (Salix alba) and blooming Wild Cherry (Prunus avium). Bieszczady Mountains, the Carpathians, Poland, May.

Grzegorz Lesniewski / Peat bog with Eurasian Aspen (Populus tremula) and Bog bilberry (Vaccinium uliginosum). Bieszczady National Park, the Carpathians, Poland, September.

Grzegorz Lesniewski / Crack Willow (Salix fragilis) and autumn snowfall. Bieszczady National Park, the Carpathians, Poland, October 2009.

Matthias Breiter / Arctic Willow (Salix arctica) catkin, Katmai National Park, Alaska

Pascal Tordeux / Poplar (Populus) trees in snow. Picardie, France December.

Pascal Tordeux / Wind-blown Willow (Salix). Le Chemin des dames, France, April.

Michael Quinton / Grizzly Bear (Ursus arctos horribilis) amid autumn willows, Alaska

Gary K. Smith / Black Poplar (Populus serotina) hybrid plantation. Suffolk, England, May.

Nigel Bean / White willow trees (Salix alba) covered in hoar frost, Somerset Levels, UK, December 2010

Nigel Bean / White willow trees (Salix alba) covered in hoar frost, Somerset Levels, UK, December 2010

Nigel Bean / White willow tree (Salix alba) covered in hoar frost, Somerset Levels, UK, December 2010

Nigel Bean / White willow tree (Salix alba) covered in hoar frost, Somerset Levels, UK, December 2010

Nigel Bean / White willow trees (Salix alba) covered in hoar frost, Somerset Levels, UK, December 2010

Terry Whittaker / 2020VISION / Willow (Salix fragilis) seed dispersal, Rutland Water, Rutland, UK, April

Terry Whittaker / 2020VISION / Willow (Salix fragilis) seed dispersal, Rutland Water, Rutland, UK, April

Terry Whittaker / 2020VISION / Willow (Salix fragilis) seed dispersal, Rutland Water, Rutland, UK, April

Bryan and Cherry Alexander / Trailing arctic willow (Salix arctophila) in the autumn with yellow leaves and exploding seed heads. Scoresbysund, East Greenland, September.

Philippe Clement / Town park along canal showing golden weeping willows (Salix vitellina var. pendula) and block of flats. Ghent, Belgium, April 2011.

Konrad Wothe / Peacock Butterfly (Inachis io) feeding on Willow (Salix sp), Bavaria, Germany

Colin Monteath / Willow (Salix sp) and Cottonwood (Populus sp) trees in fall colors with Lake Pukaki and Mount Cook, Mackenzie Country, South Canterbury, New Zealand

Colin Monteath / Willow (Salix sp) trees in fall colors with Lake Pukaki and Mount Cook, Mackenzie Country, South Canterbury, New Zealand

Brent Stephenson / Polar Willow (Salix polaris) with catkins. Blomstrandhalvoya, Krossfjord, Svalbard, July.

Yva Momatiuk & John Eastcott / Maple (Acer sp) and Cottonwood (Populus sp) trees in fall colors, Zion National Park, Utah

Yva Momatiuk & John Eastcott / Glacial pond on tundra with willows, Alaska

Simon Colmer / Goat willow (Salix caprea) buds in winter against white background, UK

Will Watson / Hoar frost with reflections of Crack Willow (Salix fragilis) in River Avon mill-leat. Warwick Castle, England, December 2010.

Bryan and Cherry Alexander / Young Nenets woman chopping Willow (Salix genus) to be used for firewood. Gydan Peninsula, Yamal, Western Siberia, Russia, 2000.

Bruno D'Amicis / Dwarf Willow (Salix herbacea) foliage. Western Tatras, Slovakia, June.

Nick Upton / Fallen willow tree (Salix sp.) at the edge of a frozen lake. Chew Valley Lake, UK, January

Nick Upton / Living and fallen moss-covered Willow trees (Salix sp.) in front of a reed bed (Phragmites australis), and frozen lake edge. Chew Valley Lake, UK, January

Ross Hoddinott / Pussy willow / Great sallow (Salix caprea) catkins, backlit, against a black background. Broxwater, Cornwall, UK, April

Florian Möllers / Fallen Willow tree (Salix sp) besdie the Tegeler Fliesstal river, Berlin, Germany, February

Florian Möllers / Willow flowers (Salix sp) amongst trunks of Birch trees (Betula sp), Germany, May

Florian Möllers / Willow flowers (Salix sp) amongst trunks of Birch trees (Betula sp), Germany, May

Florian Möllers / Fresh snow on willow catkins (Salix sp) Berlin, Germany, March

Yva Momatiuk & John Eastcott / Gray Wolf (Canis lupus) sub-adult amid willows, Denali National Park, Alaska

Yva Momatiuk & John Eastcott / Dall's Sheep (Ovis dalli) sub-adult ram nibbling on Dwarf Willow (Salix herbacea), Denali National Park, Alaska

Matthias Breiter / Cottonwood (Populus sp) trees with new leaves, Stikine River, Alaska

Konstantin Mikhailov / Dwarf polar willow (Salix sp) in the mountainous tundra of Altai Region, Russia, June, 3000 m

Daniel Heuclin / Rio Grande Cottonwood tree (Populus fremonti wislizenii) on a sand "pedestal" White Sands Natinal Monument. New-Mexico, USA, August 2009

Bryan and Cherry Alexander / Sedges (Carex sp), Willow (Salix genus) and Cotton grass (Eriophorum sp) on summer tundra. Yamal, Siberia, Russia, 1993.

Juan Carlos Munoz / Close up of bark of White poplar tree (Populus alba) Donana NP, Huelva, Andalucia, Spain

Juan Carlos Munoz / Close up of bark of White poplar tree (Populus alba) Donana NP, Huelva, Andalucia, Spain

Nick Upton / Hoverfly (Syrphus vitripennis) feeding on Weeping Willow catkin (Salix sp.) Wiltshire garden, UK, April.

Eric Baccega / Arctic willow (Salix arctica) flowering, Baffin Island, Nunavut, Canada, August

Eric Baccega / Arctic willow (Salix arctica) flowering on rocks, Baffin Island, Nunavut, Canada, August 2010

Philippe Clement / Goat / Pussy willow / Great sallow branch (Salix caprea) with female catkins, Belgium

Philippe Clement / Goat / Pussy willow / Great sallow branch (Salix caprea) with male catkins, Belgium

John Cancalosi / Osier stems (Salix viminalis) covered in hoar frost, Warwickshire, England, UK

Adrian Davies / Newly laid Willow (Salix) hedge, England, UK

Adrian Davies / Newly laid Willow (Salix) hedge, England, UK

Colin Varndell / Close up of female Grey willow catkin (Salix cinerea) Dorset, UK

Michael Quinton / Common Redpoll (Carduelis flammea) male on willow, Alaska

Steven Kazlowski / Polar willow (Salix polaris) growing on the tundra in summer, St. Jonsfjord, west coast of Svalbard, Norway.

Niall Benvie / MYN / Woolly willow (Salix lanata) catkins, Scotland

Niall Benvie / Woolly willow (Salix lanata) catkins, Scotland

Peter Lewis / Pussy willow catkins (Salix caprea) New Forest, Hampshire, England

Peter Lewis / Pussy willow catkins (Salix caprea) New Forest, Hampshire, England

Jean E. Roche / Flowers and leaves of Net leaved willow {Salix reticulata} Alps, France

Alan Williams / Willow Warbler (Phylloscopus trochilus) displaying on Willow branch, North Wales, UK, April.

Gerrit Vyn / Fox Sparrow (Passerella / Zonotrichia iliaca) of the "Red" subspecies zaboria, perched, Seward Peninsula, Alaska, USA, May.

Gerrit Vyn / Adult male Bluethroat (Luscinia svecica) in breeding plumage singing from a spring willow. Seward Peninsula, Alaska, USA, June.

Donald M. Jones / Great Horned Owl (Bubo virginianus) in cottonwood tree, western Montana

Donald M. Jones / American Beaver (Castor canadensis) carrying cottonwood branches over dam, western Montana

Donald M. Jones / American Beaver (Castor canadensis) eating cottonwood leaf, western Montana

Yva Momatiuk & John Eastcott / Northern Hawk Owl (Surnia ulula) sitting on willow branch, Denali National Park, Alaska

Yva Momatiuk & John Eastcott / Dall's Sheep (Ovis dalli) rams feeding together on golden willow leaves, Denali National Park, Alaska

Yva Momatiuk & John Eastcott / Dall's Sheep (Ovis dalli) ram browsing on golden willow leaves, Denali National Park, Alaska

Yva Momatiuk & John Eastcott / American Beaver (Castor canadensis) eating willow leaves from cut log, Denali National Park, Alaska

Andrew Walmsley / Avon river in summer with willow trees, Christchurch, New Zealand, September 2007

Andrew Walmsley / Willow tree (Salix sp) view up the trunk, Christchurch, New Zealand, September 2007

Wild Wonders of Europe / della Ferrera / Common duckweed (Lemna minor) covering a water channel at dusk, riparian forest mainly consisting of Willow trees (Salix sp) Lonjsko Polje Nature Park, Sisack-Moslavina county, Slavonia region, Posavi...

Wild Wonders of Europe / della Ferrera / Mixomicetes (Scutellina sp) on a rotten White willow (Salix alba) trunk, with some achenes, Sava river oxbows, Puska village area, Lonjsko Polje Nature Park, Ramsar Site, Croatia, June 2009

Wild Wonders of Europe / della Ferrera / Trees in flood water, mainly White willow (Salix alba) with some White mulberry (Morus alba) Aspen, Poplar and Ash trees, Kazanc area, Livanjsko Polje (karst plateau) Bosnia and Herzegovina, May 2009

Wild Wonders of Europe / della Ferrera / Mixomicetes on a rotten White willow (Salix alba) trunk, with some achenes, Sava river oxbow, Puska village area, Lonjsko Polje Nature Park, Croatia, June 2009

Wild Wonders of Europe / della Ferrera / Fallen White willow (Salix alba) in the sea, with Mussels (Mytilus sp) and Limpets (Patella sp) on trunk, Adriatic sea in the Neretljanski kanal, mouth of the Neretva river delta, Dalmatia region, Cro...

Wild Wonders of Europe / della Ferrera / Trees, mainly White willow (Salix alba) in flooded karst plateau, Livanjsko Polje, Bosnia and Herzegovina, May 2009

Wild Wonders of Europe / della Ferrera / Yellow flag iris (Iris pseudacorus) flowers and Yellow water lily (Nuphar lutea) leaves on water, with White willow (Salix alba) trees along a channel in the Hutovo Blato Nature Park, Bosnia and Herze...

Wild Wonders of Europe / Maitland / Thunderstorm over the Galicica mountain range with a Lombardy poplar (Populus nigra) silhouetted, Galicica National Park, Macedonia, Macedonia, June 2009

Colin Monteath / Willow (Salix sp) trees fringe Acheron River, North Canterbruy, New Zealand

Wild Wonders of Europe / Bergmann / Woolly willow (Salix lanata) in flower at waters edge, Thingeyjarsyslur, Iceland, June 2009

Wild Wonders of Europe / Bergmann / Woolly willow (Salix lanata) in flower at waters edge, Thingeyjarsyslur, Iceland, June 2009

Wild Wonders of Europe / D'Amicis / Mat of Dwarf willow treees (Salix herbacea) saddle in the Liptovske kopi, Western Tatras, Carpathian Mountains, Slovakia, June 2009

Wild Wonders of Europe / Bergmann / Tea leaved willow (Salix phylicifolia) Thingeyjarsyslur, Iceland, June 2009

Alan Williams / Weeping willow (Salix alba 'Tristis') on bank of River Lea, Lea Valley Park, Essex, UK, November 2006

Alan Williams / Weeping willow (Salix alba 'Tristis') on bank of River Lea, Lea Valley Park, Essex, UK, November 2006

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees in autumn, Santa Fe National Forest near Santa Fe, New Mexico

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees in autumn, Santa Fe National Forest near Santa Fe, New Mexico

Tim Fitzharris / Cooper's Hawk (Accipiter cooperii) flying over Quaking Aspen (Populus tremuloides) forest, Santa Fe National Forest, Sangre de Cristo Mountains, New Mexico

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees in autumn, Santa Fe National Forest near Santa Fe, New Mexico

Tim Fitzharris / Quaking Aspen (Populus tremuloides) and conifer forest covering Ruby Range, Raggeds Wilderness, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) forest and Mount Sneffels, San Juan Mountains, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) forest and East Beckwith Mountain, West Elk Wilderness, Colorado

Tim Fitzharris / East Beckwith Mountain reflected in pond, West Elk Wilderness, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) forest covering Ruby Range, Raggeds Wilderness, Colorado

Tim Fitzharris / Quaking Aspen (Populus tremuloides) trees and Marcellina Mountain near Crested Butte, Colorado