Populus alba var. bachofenii (Wierzb. ex Rchb.) Wesm.
Populus alba var. canescens Aiton
Populus × bachofenii Wierzb. ex Rchb.
Populus × hybrida Rchb.
Populus × canescens, the grey poplar, is a hybrid between Populus alba (white poplar) and P. tremula (common aspen). It is intermediate between its parents, with a thin grey downy coating on the leaves, which are much less deeply lobed than the leaves of P. alba. It is a very vigorous tree with marked hybrid vigour, reaching 40 metres (130 feet) tall and with a trunk diameter over 1.5 m (5 ft) – much larger than either of its parents. Most trees in cultivation are male, but female trees occur naturally and some of these are also propagated.[2]
In 1789 William Aiton described the grey poplar as a varietyofPopulus alba, P. alba var. canescens.[3] In 1804, James Edward Smith raised it to a full species, P. canescens.[1] He described differences between the leaves of the two taxa: P. alba has lobed leaves with snow-white ("niveus") undersides, whereas P. canescens has wavy-edged leaves with hoary ("incanus") undersides.[4] Later authors sometimes noted the possibility that the grey poplar was a hybrid.[5] It is now considered to be a hybrid between P. alba and P. tremula,[6] so the scientific name is written with the hybrid symbol.
