Source: Penfold, Frank. “Native Black Poplar Populus nigra betulifolia in Sussex.” Sussex Botanical Recording Society Newsletter, no. 42 (April 1996). http://www.sussexflora.org.uk/wp-content/uploads/2018/09/Newsletter_apr_1996.pdf.
At a meeting at the Linnean Society which Frances Abraham and I attended on 9th December 1993 it was resolved to set up a scheme for the conservation of this rare tree. We undertook to bring together a Working Party in Sussex, to include representatives of the Sussex Wildlife Trust, SBRS/BSBI/Plantlife, the County Councils, and the Royal Botanic Gardens (Wakehurst). A first meeting was held at Woods Mill on 24th February 1994 at which it was agreed to inspect all known specimens, to seek out and verify reports of others, to take measurements and photographs, and to consider plans for protection and propagation. Subsequently RBG Wakehurst agreed to propagate up to 1000 cuttings from verified Sussex stock and hold them for 10 years.
In all this we have relied on advice from, and identification by, Edgar Milne-Redhead, who has campaigned for many years for the conservation of this tree. We send him samples, photographs, measurements, and other data and accept his decision before inclusion on our Sussex register, with notification to the Biological Records Centre. Leading parts in the national campaign have been taken by John White of the Forestry Authority and Jonathan Spencer of English Nature.
Identification presents problems, mainly owing to the multiplicity of hybrids and cultivars. We are concerned with the Atlantic subspecies P.n.betulifolia, though the type P.n.nigra of central Europe also occurs and is difficult to distinguish. P.nigra is dioecious but the hybrids are always monoecious (male or female).
Characters to look for include a deeply-fissured and bossed trunk, downward-arching branches, and leaf margins with rounded (not hooked) teeth. Other features, such as pubescence and glands, are more problematical. Male catkins are red, produced in late March; females are lime-green, followed in June by very downy seeds. Henry suggested that the number of anthers might be diagnostic for the sub-species.
To date we have accepted less than 30 specimens in v.c.13/14. Males greatly predominate nationally, but Sussex is notable for the high proportion of females. It is too early to circulate a definitive list, but members can see a fine example by Sheffield Bridge TQ407237. We are hoping that a programme of genetic testing by the Royal Botanic Gardens will be available within a few years. In the meantime it is suggested that the random transplanting of cuttings is undesirable for the following reasons:
- the possible uncertainty of the stock
- the risk of female scions being fertilized by hybrids
- the uncertainty of recording
- the possible choice of unsuitable locations.
Within a few years a sufficient quantity of rooted and well-grown cuttings of known provenance will be available from Wakehurst. The Sussex Wildlife Trust intends to select suitable sites in river valleys, well-spaced over the county, and to arrange for their planting, recording, protection, and monitoring.
 NB This tree died in 2002.