COTTONWEED

 Cottonweed by

Zoe Devlin

SAVING ONE OF IRELAND’S RAREST PLANTS

BY TONY MURRAY, MIKE WYSE JACKSON & NOELEEN SMYTH

Cottonweed, cluasach mhara in Irish, is a rare, coastal plant species that is known in Ireland from a single location in Co. Wexford. Its status was assessed in the 2016 Red List as ‘critically endangered’ on the basis of a population decline of over 80% and because less than 50 plants remain in the wild. It is a small, shrubby perennial, growing to around 25cm tall, which has leaves and most other parts densely covered in white, felted hairs that give it a very attractive silvery-white appearance. e tiny individual tubular orets are packed tightly together to form small, yellow ower heads which were described by Zoë Devlin in her Wild owers of Ireland as “ u y buttons”.

In September 2018 a er the hot summer, sta at the National Botanic Gardens went on an autumnal expedition with the National Parks and Wildlife Service (NPWS) staff to see how the largely Mediterranean-distributed cottonweed had fared in the summer. During that visit we were shocked that just 12 individuals remained at its sole Irish location, down from the 32 recorded in 2014, and that it was on the very brink of extinction in Ireland. Since 2018 a further two individuals have disappeared and as of 2021 only 10 remain.

Apart from Wexford, where it was rst noted in 1866, it has been recorded from three Irish counties: Wicklow, Waterford and Kerry. It has, thus, been clinging on here in Ireland for very many years and while it is long gone from counties Kerry and Waterford and its occurrence in Wicklow was short-lived, its decline in Co. Wexford, where it was thriving up to the 1980s, has been dramatic.

Cottonweed is a species of coastal strandlines, gravel banks and sand dunes. It occurs in open areas on coarse, sandy gravels and does not thrive on fine-grained sandy sediments, which tend to favour the growth of marram, a vigorous species that will completely outcompete cottonweed. The remaining plants of cottonweed occur in a vegetation community that includes common coastal species such as rock samphire, sea holly, sea sandwort and autumn hawkbit.

The NPWS has been monitoring the Co. Wexford population of the species since the 1980s and from 2016 has undertaken a programme to remove marram from part of the area in which the species formerly occurred, and to replace the finegrained sands that have accumulated there with sandy gravels, the preferred substrate of the species. In tandem, the NPWS carried out ex-situ propagation of seed and cutting material of the species collected from the remaining wild population, and from 2017 has returned

young plants to a prepared plot located within an area in which the species formerly occurred. This plot was extended in 2020.

At the National Botanic Gardens the then nursery manager Edel McDonald Maher started growing the species, under licence, in the 1990s. Edel has since retired but continues to propagate the species and to visit the site regularly. Current National Botanic Gardens horticultural staff, Michael Higgins, Sean Kelly, Brian Kelly and Joan Rodgers, have been busy propagating and tending to the cottonweed collections at the National Botanic Gardens. Since September 2018 efforts have intensified to grow material for augmenting the population in Co. Wexford.

In September 2018 National Botanic Gardens staff planted nine additional plants into the plot prepared with new gravel substrate by NPWS in 2017, with eight of these surviving through the winter of 2019 - things were looking very hopeful. Buoyed up by this success, further plantings of seedlings and small plants into the prepared plot followed in each year since. Much has been learnt along the way, for example, some of the very small seedlings we planted did not survive but larger, one-year-old plants grown in pots did. Currently there are 72 adult plants growing on site (62 planted in the prepared plot with 10 naturallyoccurring, outside) where in 2014 there were just 12. On the 20th September 2021 we were delighted to discover the first crop of naturally regenerating seedlings (we counted over 60 small seedlings!) that had arisen from seed shed by plants that had been planted into the plot. We are very excited to see this natural regeneration and are encouraged that we are on the right track. It is to be hoped that the bulk of these seedlings will survive the winter and develop into mature plants and that the presence of these signals the start of a journey back from the brink for the species.

This work helps to fulfil one of the aims of the National Biodiversity Action Plan i.e. to develop conservation programmes for our rarest plant species. As this is a Mediterranean species at the edge of its range here in Ireland some of the predicted future climate change scenarios could lead to an increase in the range of the species. On the other hand, the predicted stormier conditions and sea level rise could wipe out any such gains made, and the future of this species must still be regarded as on a knife edge. We will continue the work in 2022 and beyond in the hope that this will allow this fascinating and beautiful member of the Irish flora to survive and thrive into the future.

Noeleen Smyth is formerly of the National Botanic Gardens, now at University College Dublin. Tony Murray and Mike Wyse Jackson work for the NPWS.

PHOTOGRAPHS: NOELEEN SMYTH