A plant name mystery has been discovered in the Conservation Scheme database. In January Cathy Rollinson posted on the Conservation Scheme Facebook page that the plant we list as Persicaria runcinata Needham’s form is probably really Persicaria sinuata. She found this after reading the description on the website of Growild Nursery, which now lists it as Persicaria sinuata EN.
So which is it?
Persicaria runcinata Needham's form
I did a little research, but the information I found did not provide a definitive answer. First of all, the only nursery listed for it in my copy of the Plant Finder is Growild. A search on-line confirmed this was the only available source in the UK, but there were several nurseries in France that had it. They are selling it under the name Persicaria runcinata Needham’s form, not Persicaria sinuata. Interestingly, I could find quite a few photos from Pinterest and Instagram which appeared to be our plant. Who are these mystery growers and where did they get their plants?
Looking for some authoritative source to determine the correct name, I came across the website www.flowersofindia.net. This had more detailed descriptions for both species. It listed Persicaria runcinata, common name Lobed Leaf Knotweed, as a perennial herb with stout rhizomes, stems nearly erect or ascending, 1-2 feet tall. Flowers are pinkish or white. The Conservation Scheme plant is a trailing plant, with mid-green leaves on red stems and clear pink flowers.
Persicaria sinuata, on the other hand, has the common name Red-Stem Knotweed. It says it is a prostrate annual herb with slender striped, brownish or reddish stems, rooting at nodes. Flowers are pink, and it is often confused with Lobed Leaf Knotweed. Photos of P. sinuata on the Flowers of India website look most like our conservation scheme plant, with round pink flowers. The photos for Persicaria runcinata are very similar, but stalks are green rather than red, and the flower is more white and not as rounded.
The conclusion I lean to is that the conservation plant is really Persicaria sinuata, but what about its description as an annual? The plants that both Jan and I grew have died. We presumed it was because they got too dry, but were the plants just doing what they were supposed to? The plant was introduced into the scheme in 2017, and I didn’t acquire mine until 2019, so it was persisting somewhere. David from the Cheshire & Friends group said his had flowered well, but was too vigorous.
The naming question has raised another issue with this plant. Is it really a pure species, and should we be conserving species in the scheme? The objective of the Conservation Scheme is to preserve hardy herbaceous perennials. This is usually taken to mean cultivars. We specifically ask people not to propagate their plants by seed in order to preserve the distinctive features of the plants. But what about a plant that is only available from one nursery in the UK, and only available as seed? Indeed, the original plant that Edward Needham brought back from his plant hunting in Nepal was most probably as seed, because that is how he collected. This question will need to be discussed at a future meeting with the local co-ordinators. And the mystery of its name continues.