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| The classic outline of stately White Willows (Salix alba) in the Yare Valley at Buckenham, Norfolk |
We probably all have a clear image in our minds of what a willow is when we hear mention of this group of plants. Most people will immediately envisage a large tree on a riverbank, perhaps leaning out over the water and casting interesting shadows and reflections. Some may also picture the wonderful golden colours of a weeping willow beside an ornamental duck pond. While these are classic images of willows, this group of plants also includes lower, bushy plants - collectively known as sallows - which are plentiful in almost any type of wet ground and are often the first woody perennials to colonise damp ground that has been cleared or is drying out due to habitat succession. And there are even smaller species - less than waist high - that grow in coastal dune habitats, while high in the Arctic, willows hug the ground to cope with extreme growing conditions.
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| A low, spreading mound of Creeping Willow (Salix repens) in the dunes at Holkham, Norfolk |
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| Globally, willows are surprisingly variable. In the high Arctic, Net-leaved Willow (Salix reticulata) grows to barely 10cm in height and produces little, upright catkins above whorls of rounded leaves. I photographed this one a few years ago in Alaska, USA. |
Willows are related to poplars and share a few features with them, such as the presence of stipules at the base of the young leaves and petalless flowers that are wind pollinated and clustered together in catkins. Male and female flowers appear on separate plants and those of the sallows seem to be especially popular with bumblebees in the spring.
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| This close-up of an Almond Willow (Salix triandra) stem shows one of a pair of leaf-like structures known as stipules. These structures are a useful feature in a handful of plant families and can help with species identification. |
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| Male catkin of Goat Willow (Salix caprea). Each single flower is topped with yellow stamens; the number of stamens per flower can sometimes by useful for identification. |
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| Female catkin of Grey Willow (Salix cinerea). Each single flower is accompanied by a dark bract and topped with the two-lobed, cream-coloured stigma. |
The species of willow that occur in East Anglia are mostly fairly easy to tell apart, but identification of the sallows is complicated by the freedom with which the various species hybridise. These hybrids can be fertile and further hybridise with other species, potentially creating a bewildering array of forms. We have many uses for sallows and their wood and for this reason, hybrids have been produced commercially and are widely planted in the countryside, further complicating the issue for the would-be botanist. Sometimes, it can be very tempting to quietly move away and go and look at something else!
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| The golden curtains of branches are very attractive and make Weeping Willows (Salix x sepulcralis) a popular choice next to water in large gardens, parks and municipal plantings. A number of these trees can be seen along the banks of the River Wensum in the centre of Norwich. |
