Willow

There are 400 species of willow, Salix, ranging from trees to sub shrubs, and hybrids are common. There could be many more as they are difficult to identify.  You would require a good tree ID book in order to identify them.
 
The leaves are frequently elongated but some species have round or oval leaves.

leaves

 Goat willow leaves

 catkins

Goat willow catkins March

catkins

Catkins, later in March

catkins

male catkins

Male goat willow catkins April

 female catkins

Female goat willow catkins April

Catkins June

Seeded catkins June

Further reading

 Willows  The Genus Salix - Christopher Newsholme.

Comments on this article

frank 26 January, 2012

This is most interesting

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