Willows

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.

A low, spreading mound of Creeping Willow (Salix repens) in the dunes at Holkham, Norfolk

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.

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.

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.

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!

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.

Populated by Poplars!

Straight lines of Balsam Spire Poplar are a common sight in the East Anglian region, where they are widely used for windbreaks, shelterbelts and screening.

Wherever you go in East Anglia, it's difficult to not be within sight of a poplar or two. These trees have long been popular (sorry!) as a source of quick-growing timber and most species do best in damp soils, so the open expanses of the Broads and the Fens were obvious places for them to be planted in large number. Indeed, Britain's largest poplar plantation once existed in Lakenheath Fen - some two square miles of planted poplar hybrids which became famous for its population of breeding Golden Orioles for a while.

Poplars have long been useful to mankind and this has resulted in much time and investment in producing ever more useful forms. The horticultural industry has produced an array of hybrids, in particular by crossing North American poplar species with the European Black Poplar and the resulting hybrids have been crossed again with each other to produce startlingly vigorous trees. In more recent times, efforts have been applied to producing varieties that are more resistent to certain diseases of poplars with the result that many trees we might find in the wider countryside cannot safely be identified to variety, but they can still be recognised as being Hybrid Black Poplars.

Patterns of diamond-shaped studs are an attractive feature of some poplars, including our native European Aspen.

Most poplars that you come across in East Anglia will be planted hybrids, or selected varieties of introduced species. As well as the varieties that are grown in regimented ranks in plantations on wet soils, other varieties are used as fast-growing screens to hide unsightly industrial buildings from residential areas, or as windbreaks to protect crops or to shield sports grounds. In the case of windbreaks, narrow, columnar varieties are typically selected.

But, as well as all these fast growing hybrids, we have our own native species. The European Aspen can still be found in many woods and along old green lanes and hedgelines across the region, especially on the heavier boulder clays that cover much of south Norfolk and mid Suffolk. Aspen suckers freely and can form open thickets, its leaves being very eye-catching as they tremble in the wind - hence the saying 'quaking like an aspen'. Our other native species is the Black Poplar, a species for which East Anglia holds a significant proportion of the British population. Black Poplars became very rare at one point and efforts were made to boost the population with new plantings. So young trees can now be found quite widely in the region, but the venerable old grandmothers and grandfathers are very much worth seeking out for their individuality and beauty. They stand like wizzened old people, singly in hedgerows and on village greens, or in small groups in the broader river floodplains.

The vast majority of native Black Poplars in our region are male, while female plants are very rare. This may at least in part be due to the intolerance of some people to the clouds of fluffy seeds that the female trees produce. This characterful old lady stands on the common at Old Buckenham, Norfolk.

Poplars are at their best in spring when they are at their most vibrant. First the flowers emerge - little catkins that dangle from the branch tips and waggle in the wind like lamb's tails. Poplars are wind-pollinated, so their flowers are highly mobile to allow the pollen to shake out easily, while they tend to appear before the leaves so that there is less hinderance to pollen distribution and reception. All poplar trees bear either male flowers or female flowers, but not both. The species poplars will have both male and female trees out there in the landscape, but hybrids that are named, selected clones will all be of a single sex and this can help with their identification.

Female flowers of Black Poplar. The female catkins tend to be a little shorter and less mobile than the male catkins and are greenish yellow in colour. 

A close-up of a female catkin reveals the swollen, creamy-white tips to the stigmas, waiting to receive airborne pollen from the male flowers.

Male flowers of Hybrid Black Poplar. The male catkins are dark red in colour due to the colour of the stamens which make up the bulk of the petalless flowers. The catkins are long and highly mobile in the wind, which ensures that the pollen gets shaken out easily.

Soon after the poplar flowers come the leaves. Many of the poplar hybrids have leaves that are washed with rich shades of copper, pink or yellowish-brown and really stand out in the landscape at this time. The leaves gradually become green as they open, but continue to be eye-catching as many of them have flattened leaf stalks that cause the leaf to bend against the wind in a certain way and thus flutter in the breeze.

The bronze- or copper-tinted, emerging leaves of poplars are eye-catching in spring against the backdrop of greens from other plant species. These Hybrid Black Poplars along the River Lark in Suffolk are probably the cultivar 'Robusta', which is particularly colourful in spring.

Poplar time will soon be on us, so I've just put up the poplars page on the website:

http://webidguides.com/_templates/treegroup_populus.html

My favourite East Anglian poplars - the group of old Black Poplars on Icklingham Plains in Suffolk are a wonderful sight.