Four Urban Poplars with all images and text taken from the book Field Guide to the Trees of Britain and Europe published by Reed New Holland in 2017, author Alan Birkett and ISBN 9781921517839.
Poplars have male catkins that release pollen in late March and early April. They open before the leaves so are easy to see. The first photo shows the male catkins of an Aspen. This is a Poplar that tolerates cold conditions. It is a smaller tree than most Poplars. It is a species that grows in cool regions across the whole of Europe and west Asia. (The American Aspen is a different species). It is more likely to be found in the north and west of Britain and is common in the Scottish Highlands. It is typically found in oak or birch woodland. It can spread by sending suckers up from its roots. Male and female flowers are on separate trees. The second photo shows the male catkin of a Grey Poplar. This is a natural hybrid between the White Poplar and the Aspen. It may have been introduced. It has a wide distribution in Europe and Western Asia. It is common throughout Britain. It is easily confused with the White Poplar but it grows faster and becomes a larger tree. Because the tree is a hybrid it may show aspects of both parents.
The first photo shows the male catkins of a Black Poplar. This is a large tree, native to Northwest Europe, including England and Wales where it is usually found as the variety ‘betulifolia’. It is endangered. It is common in the Vale of Aylesbury and in Manchester but rare elsewhere. This odd distribution is probably the result of local planting for timber. The tree is generally found growing close to water and nearly always leans. The bark is distinctive. Old trees have deep cracks that swirl round the trunk. Most of the trees are male and bear colourful catkins in spring. In 2002 there were estimated to be 7000 trees in the whole of the UK with only 600 females. This was probably an underestimate so there may be as many as 15,000 trees left in the UK but a disease known as “Scab” is attacking the ones growing near Manchester.
The second photo shows the catkins of a Hybrid Black Poplar. These hybrids arise when the European Black Poplar is crossed with the American Eastern Cottonwood. Some hybrids are natural but many are artificial. Hybrid Black Poplars are common. Some have been planted for timber production but others have been planted in large numbers in new towns and developments because they grow rapidly. They are generally known by their ‘cultivated variety’ name such as ‘Robusta’, ‘Regenerata’, ‘Serotina’, ‘Eugenei’ etc.