29 June 2010
Of the three species of wintergreen found in Britain, two can be found in West Glamorgan. One of them, Round-leaved Wintergreen (Pyrola rotundifolia), is a species of coastal dune slacks, growing with Creeping Willow (Salix repens). The other, Lesser Wintergreen (Pyrola minor), was once a less common plant in South Wales. In fact, until recently, it was only known from a very old record made by the famous botanist Joseph Hooker in 1846 from the head of the Neath Valley. In more recent times, Lesser Wintergreen has been discovered in the vicinity of conifer forest near Pembrey and then 12 years ago it was found in a remarkable area of willow scrub near the Amazon site at Jersey Marine. Two features that distinguished this willow scrub area were the occurrence of a very large population of Yellow Bird’s-nest (Monotropa hypopitys) and a high diversity of macroscopic fungi (toadstools). Sadly, most of this scrub was destroyed when the Amazon site was developed and none of the Yellow Bird’s-nest was saved, despite the fact that it is a UK BAP species. However a very small area of scrub was spared destruction and a population of Lesser Wintergreen survives there still (photograph above). More recent discoveries of Lesser Wintergreen in the vicinity of conifer plantation in the Neath Valley and at Whitford, suggest that this species may be increasing in the county.
The biology of Yellow Bird’s-nest and Lesser Wintergreen is fascinating. The roots of both form an intimate relationship with a fungus (e.g. Tricholoma species), which in turn forms a close relationship with a tree. In my experience, Lesser Wintergreen is often associated with willows, even when it appears to be associated with conifers. Furthermore, it seems to grow in places where the fungus, Tricholoma cingulatum, also occurs. This fungus (which is called the Girdled Knight) forms an ectomycorrhizal association with the roots of willows (including Creeping Willow) and, in my opinion, probably forms an association with the roots of Lesser Wintergreen too. When this happens, the wintergreen and the willow are connected by a fungal bridge, across which nutrients can pass from tree to wintergreen via the fungal mycelium. Something similar happens with Yellow Bird’s-nest too. In fact, for that species this is a form of parasitism that it is absolutely dependent on. Lastly, it is probably no coincidence that Round-leaved Wintergreen grows in association with Creeping Willow in dune slacks, where similar, shared mycorrhizal associations are possible.
Photo and text by Charles Hipkin.