New life for the rare cotton-trees of Suffolk

Black poplar restoration

The magnificent black poplar trees have become increasingly rare in the landscape over time due to several factors. Helen Bynum from the Suffolk Tree Wardens Network explains more about these magnificent trees, why their numbers dwindled, and the exciting new interventions that are being carried out to conserve and restore Suffolk’s cotton-trees.

Suffolk’s black poplars (Populus nigra subsp betulifolia) were known as cotton-trees for the white fluffy seeds which would have filled the air in late summer. Among natural stands of black poplar, the wind carried pollen from the male trees’ red catkins to fertilise the female trees’ yellow-green ones. These ripened into strings of green pods before bursting and releasing the wind-borne seeds. 

If wind was vital for pollination and seed spread, it was water that provided the next essential element in the tree’s life course. Though produced in huge numbers, successful seed needed specific conditions on wet river margins with freshly exposed mud that didn’t dry too quickly. 

Land drainage dried the land and flood prevention straightened and deepened river courses, removing the muddy meanders that profited the black poplars. People didn’t like all that fluff either, so although they continued to plant these very useful timber trees, often as standards in hedgerows, it was by taking cuttings from male trees. 

It turned out that similar species of continental poplars gave useful wood and were faster growing, and they readily interbred with the native species. After the arrival of the European species in the late eighteenth century, non-natives, hybrids, and clones came to dominate the landscape. 

For the native black poplar this meant a diminishing, ageing population which was heavily biased to the male gender and genetically very similar. Today such a population is unlikely to naturally regenerate easily through sexual reproduction. So, gene mixing is out, increasing the risk of a pathogen or climate shift devastating the remaining trees. 

If we had put our hands onto the landscape to the cost of the native black poplar it has also proved possible to begin to mitigate the past harm. This involves restoring field floodplains and propagating trees. 

The Dedham Vale AONB team have been collecting a range of black poplar tree material with detailed genetic provenance recorded and established a clone bank from their chosen cuttings. With the aid of volunteer planters, some 500 black poplars from here have already begun repopulating the Stour Valley.

In an exciting new collaboration with the Suffolk Tree Warden Network (STWN) the AONB team are passing on material from their trees to establish a new black poplar nursery. Members of the STWN have established a series of tree nurseries thanks to Suffolk County Council’s Suffolk 2020 fund. 

Tree wardens David Appleton and Fe Morris have already successfully included some black poplar cuttings in their nurseries but the partnership with the AONB represents a significant contribution to black poplar conservation outside the AONB. 

The new dedicated black poplar nursery will be located at Langham Hall Walled Garden, run by the experienced Steve Adams and Catherine Supple with their volunteer team.

The intention is to carefully record striking of cuttings from the AONB marked stock so progeny can be available for river and wetland restoration throughout the county. In addition to the nursery, two carefully selected male and female feather trees will be planted in a nearby river-meadow floodplain, in an area that’s managed to ensure the best chance of natural regeneration and successful seed germination. 

Black poplars become sexually mature from around six to ten years, so this forward-looking project will take the best of East Anglia’s native black poplar stock from the AONB and give it an enhanced chance via the STWN to help future proof Suffolk’s cotton-trees.

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