Belfast Botanic Gardens Tree Archive

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This series of short articles about trees in the Belfast Botanic Gardens is compiled by members of the Friends group and Gardens staff. We aim to build up to a comprehensive archive of trees in Belfast Botanic Gardens. Each article illustrates a tree growing in Belfast Botanic Gardens together with information from a range of sources. Where possible we will give the tree tag number - these are the small aluminium discs, usually fixed on the tree trunk, 2 to 3m above ground level.
Salix x sepulcralis 'Chrysocoma'
Weeping willow

Tag -
54 deg 34.873N
5 deg 55.902W

Two types of weeping willows are commonly seen in Ireland. Salix caprea ''Pendula', the weeping goat willow or 'pussy willow' is a unprepossessing tree of urban front gardens. Its branches are thick and stiff and the tree seldom attains an elegant shape. In contrast, the weeping Babylon willow is a superb elegant tree, although eventually becoming too large for a small garden. The species Salix babylonica is not reliably hardy, but a cross between it and Salix alba is much hardier. It is this cross that is widely grown in Ireland. It is now known as Salix x sepulcralis, although you will find many other names in popular tree books.

The weeping willows growing in Belfast Botanic Gardens are the variety 'Chrysocoma' a form with bright yellow twigs in early spring. The golden weeping willow was introduced to the UK around 1908 perhaps from Germany. The Babylon willow has nothing to do with Babylon - it is a native of China.

Popular tree books and even more so the World Wide Web, are full of confusion concerning willows and this one in particular. Willows, like hazel and alders, have catkins. Catkins are a normal feature of trees that are wind pollinated yet willows are described as insect pollinated. This is based on the fact that the individual flowers in the catkins produce nectar - which would clearly be of no value to a wind-pollinated tree. The truth is probably more complex. A study of Japanese willows suggested that in fine weather wind pollination was more important for seed production whereas in a wet and cloudy spring high seed set depends more on insect pollination

Willows are normally dioecious - that is they have male and female catkins on different trees. The weeping willow is described as an infertile male clone. However, as you can easily see on the trees in the Botanic Gardens, the weeping willow produces both male and female catkins on the same tree. Whether or not the clone is infertile, as are many interspecific hybrids, seems unclear. An Australian government web-site describes the weeping willow as sometimes producing seed and therefore a potential threat to wild habitats. So it seems that under certain circumstances this hybrid may produce viable seeds

As the photographs below show the differences between the male and female catkins are quite distinctive.

Salix x sepulcralis in Belfast Botanic Gardens

Catkins on Salix x sepulcralis

Mature weeping willow in Belfast Botanic Gardens branches of weeping willow with catkins

female catkin of Salix x sepulcralis

detail of male catkin Salix x sepulcralis

female catkin male catkin - detail

female catkin and stigmas of Salix x sepulcralis

salix x sepulcralis single stigma and single anther

female catkin - detail showing stigmas single stigma (left) and single anther from weeping willow catkins

Photos taken in Belfast Botanic Gardens in 2009. Copyright: Friends of Belfast Botanic Gardens.

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