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I’ve been spending a lot of time reading what little information there is on One-flowered Wintergreen, Moneses uniflora, doing site visits, and chatting with other experts. I’ve been trying to figure out what has caused its sharp decline in abundance and distribution globally, and how we can help prevent it here in Scotland.  

The uncomfortable answer I’ve come to is that we still don’t really know all that well. Around 10% of the Scottish population is in the Cairngorms, the rest distributed sparsely across the Highlands. In the last 50 years, I estimate that we’ve lost half of our populations, and of those remaining, only a few are stable or improving. We may soon lose all One-flowered Wintergreen in the UK without intervention. 

White bell like flowers called One Flowered Wintergreen

Saving One-flowered Wintergreen

Thousands of years ago, before significant human alteration to the landscape of Britain, perhaps One-flowered Wintergreen existed in a particular niche. It may have relied on the bare ground made by a wild boar digging for roots in the woodland, or the wood pulp made by a beaver chopping a tree, or the trampled ground under the hoof a mighty Auroch. 

In the modern world humans create this niche for them more than animals, and sadly, our modern management of pine woods has favoured it less. Through research and collaboration, we will be able to manage woodlands holistically, providing a mosaic of habitat for One-flowered Wintergreen in Scottish pinewoods, as well as other rare native species. 

In Autumn 2023 we translocated 109 individual One-flowered Wintergreen rosettes from two sites in to RSPB Abernethy, reinforcing a tiny relic population. This is a very early trial, as much a learning experience for future work, as it is to improve the condition of the Abernethy population.

I have been cautious to publicise this work, as, given no one has ever translocated One-flowered Wintergreen before (or even worked towards conservation of this species), I was prepared for total failure. However, the good news is, after 9 months at their new site, survival of rosettes remains above 70%. This is excellent for a plant translocation and bodes well for further Wintergreen translocations.

We hope to do more translocations to allow genetic mixing between populations and to rescue them from threatened sites. In addition to collecting plants for translocation, 12 plants went to Royal Botanic Gardens Edinburgh, where they have been working towards understanding the complex fungal interactions which One-flowered Wintergreen relies upon to survive, and in particular, to germinate.

Why is One-flowered Wintergreen in trouble? 

One-flowered Wintergreen is the only member of its genus Moneses, closely related to Pyrola, a group containing the other wintergreens, such as Intermediate Wintergreen (Pyrola media). Sadly, all are rare and in decline.  

True wintergreens are partial-mycoheterotrophs, which means that they have an alternative to photosynthesis for acquiring their energy to grow. They can parasitically take sugars and other minerals from fungus in woodland soils.

This ability to uptake energy from the soil as a supplement to their photosynthesis is likely part of why they are so challenging to understand and to propagate in captivity. There have also been suggestions that the presence of specific fungi is necessary for the tiny powder like seeds to germinate. 

What have we learnt?

One-flowered Wintergreen does not seem to have an easily definable niche. It is very rare, only occurring at specific sites, and often isolated to an area a few tens of metres across in a large and apparently suitable woodland.

Recently, we have had some breakthroughs helping us to understand this plant better. Trials of cattle grazing in woodland have yielded rapid recovery in a One-flowered Wintergreen population. Another site was heavily trampled and disturbed in the process of Rhododendron removal, again yielding rapid recovery of Wintergreen. These plants all seem to recover on sites where bare ground, trampled wood, and organic material are present.  

On forestry sites, One-flowered Wintergreen appears to grow only along forestry tracks and where the ground has been historically disturbed. A picture is starting to emerge of this species favouring periodic heavy disturbance of woodland soils.

Armed with this information we are providing advice to current land managers. We are also investigating options for a small-scale trial translocation of One-flowered Wintergreen, as much to aid in our learning of the needs of this rare flower, as to aid the genetic resilience of a small and struggling population.  

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