Northern Ireland's Priority Species

Polystichum lonchitis – holly-fern

 

Distribution map

Click here to view an interactive map of the Northern Ireland dataset as currently collated by CEDaR.
The map is generated through the NBN Gateway using their Interactive Mapping Tool.

 

Polystichum lonchitis (L.) Roth
Family: Dryopteridaceae

Holly Fern is an arctic-alpine species which occurs at only one site in Northern Ireland and has been recorded in just 12 hectads in Ireland post-1987.

In brief

  • Holly Fern occurs at only one place on Braade Cliff in the Lough Navar Forest Park in Fermanagh
  • The cliff in Lough Navar Forest is a north facing scarp which is the preferred habitat of the species
  • The fronds are winter-green so the plants can be seen throughout the year
  • This is the only site for Holly Fern in Northern Ireland, and in the rest of Ireland the species is rare and local. Braade Cliff is the speciesí most easterly site in Ireland. At the Braade site there are three mature plants and two more recent immature ones
  • Recently there was a fire on the scarp but the Holly Fern was unaffected and this would appear to be the main threat to the species at this site
  • The moss Orthodontium gracile has been recorded on this scarp at its only known Irish site

Species description
Holly Fern is a shiny, leathery fern with once pinnately divided fronds whose pinnae have spiny margins. The fronds grow in dense tufts and are up to 30 cm long.

Life cycle
Holly Fern is very slow growing and appears to take many years before it produces spores. One of the five Fermanagh plants was found as a mature plant in 1979 and was still in excellent condition 32 years later in 2011.

Similar species
Small or immature plants of Polystichum aculeatum (Hard Shield-fern) could be mistaken for Holly Fern. Holly Fern is once pinnate as opposed to Hard Shield-fern which is bipinnate, and the pinnae of Holly Fern are much more triangular in shape.

How to see this species
Holly Fern occurs at a near inaccessible site on the north facing, sandstone Braade Cliff in Lough Navar Forest. It should be looked for at similar sites elsewhere in Northern Ireland.

Current status
Holly Fern occurs at one site where there are five plants, three mature and two immature. Three of the plants grow on bare sandstone, and two others grow through rank vegetation; all the plants are found in a rectangle about three metres by one metre

Why is this species a priority in Northern Ireland?
Holly Fern is an Irish Red Data Book species which is rare and occurs at a single site in Northern Ireland. The species is also a UK Priority Species with a Biodiversity Action Plan.

Threats/Causes of decline
The most likely immediate threat to the species in Fermanagh is a heather or forest fire which spreads to the cliff. One such fire occurred some years ago but luckily did not affect the Holly Fern. As this is an arctic-alpine species at the southern limit of its range, global warming may affect the species in the medium to long term.

Conservation of this species

Current action

  • The species is listed in Schedule 8 of the Wildlife (NI) Order, 1985
  • The site where the species occurs is included within the designated site of Braade ASSI
  • The status of the plant is regularly monitored

Proposed objectives/actions
Ensure that the population is maintained, and if possible increased, through appropriate habitat management.

What you can do
If you think you have found this species, contact your local Biodiversity Officer .
The study of wild plants is an interesting hobby for anyone interested in the outdoors. The Botanical Society of the British Isles welcomes beginners to its field trips.
The study of ferns is an interesting hobby for anyone interested in the outdoors. The Botanical Society of the British Isles welcomes beginners to its field trips and anyone especially interested in ferns can contact the British Pteridological Society.

Further information

Links
Northern Ireland Vascular Plant Database

Literature
Preston, C.D., Pearman, D.A. & Dines, T.D. (2002). New Atlas of the British and Irish Flora. Oxford University Press, Oxford.
Page, C.N. (1982). The Ferns of Britain and Ireland. Cambridge University Press, Cambridge.

Text written by:
Robert Northridge