Plant of the Week – 29th March 2021 – Twinflower (Linnaea borealis)

LOST AND FOUND – A TWINFLOWER STORY

Linnaea borealis (Twinflower) is a nationally scarce plant, mainly restricted to the pinewoods of north-east Scotland, although it may also occur under birch and in open sites. It is found in similar habitats around the globe in the northern hemisphere and I remember seeing it growing on the campsite at Anchorage in Alaska. it is named after the great Swedish botanist Carl Linnaeus.

Twinflower is a member of the Honeysuckle family (Caprifoliaceae) and is a low-growing wintergreen perennial. It has characteristic pairs of delicate drooping pink flowers which have 4 stamens and appear between June and August. The leaves are paired, simple and toothed. The fruits are well adapted to animal dispersal with paired bracts and viscid hairs.

Linnaea borealis, Wester Colbo Wood, Highland. Photo: Brian Ballinger.

Some populations do not flower regularly and it grows best in light shade. 

In Scotland its growth appears to be mainly vegetative and it can form quite large patches.

It spreads horizontally by creeping often reddish woody stems.

it was some years before I saw twinflower in Scotland and I first located it near Golspie in Sutherland.  Here it grows close to the even rarer One-flowered Wintergreen (Moneses uniflora). I have subsequently visited sites in several other parts of Scotland.

Since taking over as Vice-county recorder for East Ross (VC106) with my late wife, my search efforts have been concentrated there.

Ursula Duncan in her 1980 Flora of East Ross-shire (published by this Society when it was the Botanical Society of Edinburgh) reported that it had not been seen for more than 20 years in Easter Ross and it was feared that it may have become extinct there. Sites at Brahan had been destroyed by cultivation, although there were also old records for Novar. The last report was from Lady Caley in The Field in 1957 at Amat.

Distribution of Linnaea borealis. The key shows the history of records. Map from the BSBI.

And, so it remained until March 2007, when my late wife and I had been asked for information about Orthilia secunda (Serrated Wintergreen) sites for a Northern Irish research project. We were directed to a possible location at Wester Culbo on the Black Isle in a Forestry Commission pine plantation. Orthilia was indeed to be seen by the path, but another plant caught my eye close by and on closer inspection there was little doubt that it was Linnaea. This was fairly large patch extending for around 40 metres and visits in the summer confirmed that it flowers well here.

There had been unconfirmed reports from estate staff of a site at Strath Vaich, but repeated visits by groups of botanists had failed to find anything. However in March 2012, Ian Green was doing a woodland survey in the area and came across Linnaea growing under birch amongst Vaccinium myrtillus (Blaeberry or Bilberry). The plants are scattered here and a subsequent summer visit with the Inverness Botany Group managed to find a couple of flowers.

In September 2015 I was looking at some under-recorded squares north of Alness for the Botanical Society of Britain and Ireland’s Atlas 2020. In a Forestry Commission pine plantation at Cnoc Navie. I ventured off the path for a short distance and to my surprise came across a large patch of Linnaea creeping along in the vegetation. Again, it proved to flower well on a summer visit in 2016. Another population has since been discovered close by.

In August 2016 Derek Gunn of the northern forestry area contacted me to say that they had found two more Linnaea patches just east of Drove Stance, in a pine plantation about 3 kilometres north of the Cnoc Navie site. And more was to follow.

In 2018 a small group was recording on the Alladale estate, aiming for some high cliffs. We stopped on the way to admire ancient pinewood and Sandy Payne scrambled up a slope and noted a small patch of Twinflower leaves. I spotted another patch and another population has been found there since. Sandy Payne and Diana Gilbert are now working on a Twinflower conservation project in the Highlands. I wonder how many more Twinflower locations await discovery.

New sites have also been reported recently in Fife and West Sutherland.

It is interesting to speculate about how Linnaea came to be in these Easter Ross locations, three of which are pine plantations. The populations appear to be genetically distinct according to preliminary investigations, so they may be relic populations rather than accidental introductions.

it is interesting to note that all these discoveries have depended on seeing the leaves rather than the flowers and in fact the plants are often easier to see when other vegetation has died back for the winter.

I would encourage visitors to northern and other pinewoods to keep an eye open for this beautiful plant. It is wintergreen and, once one is familiar with it, Linnaea has a very characteristic growth pattern, so it can be seen in winter when other vegetation may have died back.

References:

Ballinger Brian (2017) Lost and Found- Linnaea borealis (Twinflower) in Easter Ross. BSS News 108 27-28.

Duncan U. K. (1980) Flora of East Ross-shire. Botanical Society of Edinburgh.

Lusby P.S.  in Stewart A., Pearman D. A. and Preston C. D. Eds. Scarce Plants of Britain JNCC

Peterborough.

Plantlife (2011). Managing Scotland’s Pinewoods for their Wild Flowers. Plantlife Scotland Stirling.

Brian Ballinger

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