The cover image for our new issue shows Purple Toothwort (Lathraea clandestina), a holoparasitic perennial herb which is devoid of chlorophyll and can parasitize a wide range of host plants.

This cover image accompanies our newest Biological Flora of the British Isles account on Lathraea clandestina by Atkinson & Atkinson. The photograph was taken by Tony Davy, our Biological Flora Editor. Here, author Mark Atkinson shares more about this fascinating species and the process for putting together a Biological Flora account .

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It is an honour to have my Biological Flora account on the front cover, which is a very rare occurrence. Lathraea clandestina is such a photogenic plant that it is definitely justified, but it is only photogenic for a short time. Before the flowers open the shoots and flower buds can be seen. Below is a picture showing the white bracts subtending the flowering shoots and the distinctive white cross of the calyx surrounding the corolla. From when the flowers start developing to when they all finish can be around 3 months, but each flower only lasts for a week or so after it opens, so most clumps of open flowers have a few fading ones. Before flowering there is nothing to see unless you dig and even during flowering it can be overshadowed by surrounding vegetation. As soon as the flowers have been fertilised the fruits begin to swell and become very sensitive to disturbance and eventually shatter and scatter the seeds (usually 4) up to 6 or more metres.

I first saw L. clandestina at Cambridge University Botanic Garden flowering on a lawn amongst bamboo plants in the mid 1980s, and at first I thought it was purple sweet wrappers scattered on the grass! Ever since then I was hooked on it, trying to find it up and down the country. While I was in Cambridge in 1988 I looked at Coe Fen and found it there, where it still grows, where it was planted from the Botanic garden in 1908. I remember walking around a nature reserve in the Cotswolds and I met a birdwatcher. In a conversation I had with him, he couldn’t understand why I would look for a plant again if I had seen it once. The next major step in my experience of the plant was seeing it for the first time in its native habitat on the banks of the River Sioule in the Auvergne. I walked off the end of a layby with a sandwich in my hand and there it was on bare soil looking as if the area had recently been flooded.

A Biological Flora account collects together a wide range of information from distribution, climate, insect visitors, pollinators, seed germination and development; the more ecological side of things. Sometimes this information is very scattered and hard to find. I would like to give a plug here to the wonderful Biodiversity Heritage Library which makes available a wide variety of historic and modern literature at no charge. There is a research group at Nantes University where Serge Renaudin did his PhD work on the biology of L. clandestina in the 1970s and this and later work by his students and collaborators was important in this account. There is a lot of physiological and molecular material in the account which I think is important to understand its biology. Finally, I want to thank Tony Davy and his Associate Editors, who did so much to coax this account into shape.

Mark Atkinson Swansea University Medical School, UK

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You can read this full Biological Flora of the British Isles account on Lathraea clandestina here: https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2745.13473

You can access the Biological Flora of the British Isles database here.