Symphytum tuberosum – May 5th 2025 – Tuberous Comfrey
Symphytum tuberosum: the general arrangement of leaves and flowers. Image: John Grace
About a month ago I started to notice the yellow flowers of the Tuberous Comfrey Symphytum tuberosum. It flowers profusely, and much earlier than its well-known blue-flowered cousins Symphytum officinale and the hybrid Symphytum x uplandicum (‘Russian Comfrey’). The Tuberous Comfrey is a perennial with stout rhizomes, and is shorter than other comfries (less than 60 cm, usually much less). As a result of its creeping rhizomes, it forms patches. I see it mostly by roadsides, but it also occurs in ditches, on river-banks and sometimes in damp woods. It stays in flower until June and then rather abruptly dies down.
Symphytum tuberosum, showing inflorescences in situ. Image: John Grace.
Comfry belongs to the Family Boraginaceae, the family of Borage, Forget-me-not and Lungwort. Many species of Symphytum have been used in medicine. Alternative names include knitbone, boneset, and the name Symphytum is from the Greek symphytis, meaning growing together of bones, and phyton, a plant. Similarly, the common French name is consoude, meaning to weld together.
Most of the Boraginaceae have blue flowers but they can be yellow, pink, orange, blue or purple. Yellow is uncommon in this Family, although all green plants have at least a little of the yellow carotene pigment called xanthophyll. It’s a protective pigment within the photosynthetic machinery. Yellow-flowered members of this Family include Amsinckia (Fiddleneck) and the rare Nonea lutea (at just one site in Scotland).
Evidence of nectar-robbing. Holes have been bitten in the corolla wall to gain access to nectar. Image: John Grace
The flower is made up of five fused-together petals, making a tube. Long-tongued bees are the usual pollinators, but many of the flowers have been robbed of nectar by other large flying insects. As shown in the image, holes have been bitten in the wall of the flower-tube, enabling easy access to nectar. Nectar-robbing is quite a common occurrence
On the road verge in South Ayrshire. There are many of these clumps on the A77 main road and roads nearby. Image: John Grace.
Symphytum tuberosum is said to be a native plant, but we can’t be sure. Its first record in the wild was near Edinburgh, from the Water of Leith, where it can still be found. John Hope’s manuscript ‘List of Plants growing in the neighbourhood of Edinburgh’ says it grows “opposite the new wall, May 18th 1765”. This is rather a late record for a native plant and as it was known to have been cultivated in the nearby Edinburgh Physic Garden in 1683, some authors have said it is most likely to be an introduced species (Pearman 2007, Braithwaite 2021). However, Kew’s website, Plants of the World Online, still shows it as native in Britain but introduced in Ireland.
Distribution patterns of S. tuberosum. Note the detail in the southern Scotland map: many records are in lines corresponding to roads. It seems the plant is now colonising road verges. British and Irish distributions are from BSBI/Maps. Global distribution is from GBIF.
The British distribution is unusual. S. tuberosum is found mostly in lowland parts of Scotland. I wonder, has it been spreading from a hypothetical starting point on the Water of Leith? According to the BSBI Atlas 2020 it is indeed spreading, and my own observations over a 10-year period from Ayrshire suggest it is spreading rather quickly on road verges in the south-west.
Whilst walking around Ballantrae Bay in South Ayrshire I noticed a large colony next to the sea, suggesting the plant has some resistance to salt. A interesting feature of this colony is the presence of rabbit holes. Below, the picture on the left was taken on April 20th. The right-hand image was two weeks later, May 4th, at the same spot (not the same angle, sorry). I believe the rabbit is looking for a breakfast of rhizomes.
Symphytum tuberosum in a maritime setting, Ballantrae. Rabbit/s seem intent on accessing the root system. Image: John Grace
Research on this species in central Europe (Kobrlová et al. 2016) has highlighted the occurrence of several variants, based on the number of chromosomes, from diploid (2n =18) to octodecaploid cytotypes (2n = 144). I hadn’t realised until reading the article that such variation is not uncommon in the Boraginaceae: in the extreme case of Symphytum officinale the chromosome count goes from tetraploid (2n = 32) to the widespread dodecaploid (2n = 96). I have been unable to find comparable data for Britain and Ireland.
Those readers who like to forage for wild plants, should read this article by Monica Wilde.
References consulted
Braithwaite ME (2021) Scotland’s heritage of naturalised medicinal plants. British & Irish Botany 3, no. 1.
Jeiter J, Langecker S and Weigend M (2020) Towards an integrative understanding of stamen–corolla tube modifications and floral architecture in Boraginaceae ss (Boraginales). Botanical Journal of the Linnean Society 193, no. 1 (2020): 100-124.
Kobrlova L, Hroneš M, Koutecký P, Štech M, Trávníček B. (2016) Symphytum tuberosum complex in central Europe: cytogeography, morphology, ecology and taxonomy. Preslia 88, 77-112.
Pearman DA (2007) Far from any house–Assessing the status of doubtfully native species in the flora of the British Isles. Watsonia 26, 271-290.
©John Grace
