Species of the month
Twinflower (Linnaea borealis)
 Distribution map | Twinflower (Linnaea borealis) There are few plants of our native pinewoods that can wow people with their floral display, but twinflower is certainly one that can and July is the month to see it! Twinflower is a creeping woody perennial capable of considerable vegetative spread. Side shoots arise from buds along the stem enabling the plant to spread in all directions resulting in the formation of distinct patches which are characteristic of the species. Stems are creeping (up to 40cm) and red/brown in colour. Leaves are oval (4 to 16mm), in opposite pairs along the stem. Flowers are white/pink, bell-shaped (5 to 10mm long), hanging in pairs on erect leafless stems (up to 8cm). Flowering begins in mid to late June and can continue to the end of July. The species is most easily spotted when in flower, but the leaves are evergreen so it can be identified in a vegetative state at any time of year. Twinflower usually occurs in the scattered remnants of native Scots Pine woodland and old plantations, and occasionally in open birch woodland, juniper scrub and heathland. The species has been recorded at up to c. 800m in the Grampians. The typical ground layer associates are the dwarf shrubs heather (Calluna vulgaris), blaeberry (Vaccinium myrtilus) and cowberry (V. vitis-idaea), as well as wavy hair grass (Deschampsia flexuosa) and pleurocarpous mosses (Hylocomium splendens, Pleurozium shreberi and Rhytidiadelphus triquetrus). Where the cover of dwarf shrubs is high, the density of twinflower shoots is often very low which can make patches quite inconspicuous. The best flowering occurs where patches are in slight shade and is often poor or completely absent in heavily shaded patches. Twinflower benefits from disturbance and is sometimes found growing beside, or along, tracks and old timber extraction routes. It has been hypothesised that fragments of twinflower may have been spread around plantations in the past by log skidding activities. Twinflower sometimes grows in association with other pinewood specialists such as creeping lady’s-tresses (Goodyera repens), serrated wintergreen (Orthilia secunda), intermediate wintergreen (Pyrola media) and very occasionally the one flowered wintergreen (Moneses uniflora), so if you discover a twinflower patch it is worth keeping your eyes open for these interesting species too. Twinflower has a circumpolar distribution and is associated with the boreal forests across North America, Europe and Asia. In Britain, twinflower has undergone a considerable decline and is now almost entirely confined to the northeast of Scotland with its stronghold in the Cairngorms National Park. The loss and fragmentation of native Scots pine woodland, unsuitable woodland and heathland management practices, and reproductive isolation of single clones are the likely causes of this decline. The species is a UK Biodiversity Action Plan, Scottish Biodiversity List, and Cairngorms Local Biodiversity Action Plan priority species. Twinflower has been included as one of the four species targeted for conservation action by the new Cairngorms Rare Plants Project. Despite the profusion of flowers that are produced each year by some twinflower patches, seed production is chronically low in most Scottish populations. This is the result of reproductive isolation of patches consisting of single clonal individuals. As the plant is highly self-incompatible, i.e. it has a much reduced capacity to make seed from its own pollen, cross-pollination with a genetically different plant is required for successful seed production. Twinflower is pollinated by small muscid flies, empid flies, hoverflies and occasionally bumblebees. Remaining patches are frequently too far apart for these small insects to transport pollen between them. Although twinflower can persist and spread locally by vegetative propagation, without seed it is unable to disperse into new suitable habitat or adapt to environmental change posing a serious threat to the long-term survival and recovery of the species in Scotland. Establishing the full distribution of twinflower in the northeast of Scotland is essential to the successful future conservation of the species. A considerable number of previously unrecorded twinflower patches have been discovered on Speyside in recent years by conservation organisations and local botanists. The discovery of more new patches in both Aberdeenshire and the Cairngorms National Park is likely, especially by those venturing off the beaten track in the pinewoods of Deeside and Speyside. Andy Scobie |