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Acaena ovalifolia Ruiz & Pav., Two-spined Acaena

Account Summary

Introduction, neophyte, a rare, naturalised, garden escape.

1952; Mackechnie, R.; Killadeas Td, Lower Lough Erne.

There are three records in just two Fermanagh stations (Killadeas and Tempo Manor) for this low-growing, mat-forming, perennial garden escape. In the grounds of the Manor House Hotel at Killadeas on the shore of Lower Lough Erne it has persisted for at least 25 years, while the second location is a recent discovery along a path-side in estate woodland.

Mention of only one record of this persistent naturalised alien appears in the Revised Typescript Flora. A form of 'Pirri-pirri-burr', as members of this mainly New Zealand genus are often called, was found at Killadeas on the shore of the lough by the very reliable Scottish botanist, R. Mackechnie who was working locally for a time at Lisnarrick near Kesh. Almost all of his Fermanagh plant records appear with very limited site information. Although there is so little detail associated with this record, Mackechnie's reputation as a field botanist is so well-founded there is no reason whatever to doubt his find.

However, McClintock (1979) has pointed out that prior to the early 1970s, and the publication on this group of plants by Yeo (1973), all published records of this genus were made under the name A. anserinifolia (as used in this instance by Mackechnie), or its synonym A. sanguisorbae. Without voucher specimens, the true identity of these records cannot be known. Many of Mackechnie's records, including garden escapes, have herbarium vouchers chiefly located in the Royal Botanic Garden, Edinburgh (E) and the Kelvingrove Museum in Glasgow (GL), but a few also exist in BEL. McClintock listed the Mackechnie record and another by Paul Hackney at the Manor House Hotel, Killadeas dated 11 September 1975. Subsequently RHN discovered the plant in November 1997, naturalised by a path-side in plantation woodland at Tempo Manor, Upper Lough Erne.

Acaena is a curious genus, native primarily in New Zealand, but with a few species scattered in S America and Polynesia. Species such as A. anserinifolia (J.R. Forst. & G. Forst.) Druce (Bronze Pirri-pirri-bur), A. novae-zelandiae (Pirri-pirri-bur) and A. ovalifolia (which is S American) are commonly grown in gardens as low, ground-cover mats, suitable for planting along with smaller bulbous plants, on rockeries with alpines, or along pathways and between paving slabs (Grey-Wilson 1989, p. 13). The burr fruits attach themselves to animal coats or human clothing and records of them seem to be on the increase in B & I. Beyond the garden wall, the plants tend to occupy sparsely vegetated, somewhat disturbed ground, either in sun along wayside paths (the plants seem very well adapted to occasional droughts), or in partial shade on the margins of woods or scrub.

Threats

The plant can be invasive and forms of Acaena have become troublesome pathside weeds in a number of forest parks in NI.