Plant of the Week – April 6th 2026 – Hidcote Comfrey (Symphytum x hidcotense) – Botany in Scotland

In response to questions such as ‘what plant is that?’ we need to keep in mind the uncertainty relating to hybridisation. Plants hybridise much more frequently than animals and sometimes the hybrids become fertile. The hybrids generally are intermediate between the parents, but they may themselves interbreed and/or backcross with the parents to make a ‘hybrid swarm’ consisting of plants that look somewhat like the parents. Such phenomena can be most troublesome for field botanists, as indeed they were for the ‘Father of Plant Taxonomy’ Carl Linnaeus (1707–1778). He suffered bouts of depression and melancholy, which some people think was the result of his grappling with the idea of hybridisation.

Russian Comfrey (Symphytum x uplandicum), a cross between the native Symphytum officinale and the introduced Symphytum asperum. The plant is widespread in Britain and cultivated by organic gardeners who use it to make liquid fertilizer. Russian Comfrey is thought to be one of the parents of the more recent hybrid Symphytum x hidcotense. Image: Chris Jeffree, from last year’s blog.

In his early work Linnaeus believed that plant species were fixed and unchangeable, but from 1750 onwards he realised that hybrids do occur, and he went so far as to demonstrate that they can be created artificially (he crossed two species of Salsify). He invented the use of the multiplication sign ‘x’ to signify when a plant is a hybrid.

This week we look at hybridization within comfrey (genus Symphytum, in the Family Boraginaceae). We wrote about Russian Comfrey a year ago. It’s a hybrid between our native Symphytum officinale and the alien S. asperum. But there are several hybrids in Symphytum, and this week we move to another.

The Russian Comfrey can itself form hybrids with Creeping Comfrey (S. grandiflorum), a species from the Caucasus which is more frequent in the southern half of Britain but does occur in Scotland. The resultant plant is called Symphytum x hidcotense, with the common name ‘Hidcote Comfrey’¹. It is sometimes sold at Garden Centres, called ‘Hidcote Blue’.

Hidcote Comfrey Symphytum x hidcotense. Image: Chris Jeffree

The trouble is, the Hidcote Comfrey is so like its parent Creeping Comfrey that it is hard to tell them apart and recorders didn’t start to recognise the hybrid until 1979 – they may have recorded Symphytum x hidcotense as Creeping Comfrey S. grandiflorum.

Creeping Comfrey Symphytum grandiflorum. Image: Chris Jeffree

By a lucky chance and with a little help from the local BSBI recorder, Chris Jeffree has recently found both of them flowering at the same time in East Lothian, and so we can compare and contrast. Telling them apart ought to be easy using the key in Stace’s 4^th edition of New Flora of the British Isles. The choice is:

Either

Corolla pale yellow when open, often flushed with reddish on the outside, stems unbranched; calyx divided ¾ to 4/5way to base = S. grandiflorum

Or

Corolla predominantly blue or pink when open; lager flowering stems branched; calyx divided 3/5 to 2/3  way to base = S. x hidcotense

We invite you to examine Chris’s images and see whether you agree with our identification. To complicate matters even more, Garden Centres may have ‘’Hidcote Blue’ and ’Hidcote Red’ as both blue and red forms are found in the hybrid cross, and these will sometimes be thrown out of gardens and establish in the wild from bits of rhizome.

Hidcote Comfrey Symphytum x hidcotense. Image: Chris Jeffree

Does Symphytum x hidcotense produce viable seeds? According to Wildflowerweb “Any fruit consists of small, hard nutlets, but they often fail to develop fully or are infertile. Instead, the plant spreads mainly through rhizomes, making seed dispersal largely irrelevant in cultivation or naturalisation. This vegetative spread allows it to form robust, spreading clumps over time in favourable conditions”.

Creeping Comfrey Symphytum grandiflorum. Image: Chris Jeffree

For Symphytum x hidcotense, I browsed the BSBI data base to see how often it had been recorded in Scotland. There are around 70 records, the earliest being 1994. Here are some of the locations: Monktonhall Bing near Millerhill, Water of Leith, Dornoch, Yellowcraig (East Lothian), Jedburgh, Balerno, Mortonhall,, Glasgow, West Linton. Sometimes the locations are woodland.

Hidcote Comfrey Symphytum x hidcotense. Image: Chris Jeffree

Hybrids made by crossing any closely related species are usually infertile, but an infertile hybrid can become fertile after doubling of the chromosome number to produce polyploid plants². Then, a completely new species that cannot breed with either parent is formed. This must have happened many thousands of times in the long evolution of flowering plants but, as Milne (2025) points out, it has been reported only a few times in the last 500 years³. Recent examples are the formation of Senecio eboracensis and Mimulus peregrinus (Lowe and Abbott 2003, Vallejo-Marín M. 2012). Others may have occurred but gone un-noticed. Many of the new species were probably ill-adapted to their environment and so died out.

European distribution of Hidcote Comfrey Symphytum x hidcotense, from GBIF.

Opportunities for hybridisation occur more often in urban situations where species from far-way regions are continuously being introduced as garden plants, and habitat disturbance is frequent. Data showing this are included as maps in Stace et al. (2015). They distinguish between ‘spontaneous hybrids’ and ‘introduced hybrids’. Both are especially frequent in the heavily-populated lowland regions of Britain; and the pattern in Scotland is clear: there are far more hybrids in the Central Belt (the lowlands between Glasgow and Edinburgh), and many in the smaller settlements on the eastern side of the country.

Detecting new cases of hybridisation in wild populations is the task of highly skilled recorders, who examine their specimens astutely. Most of us haven’t reached this level, and we tend to shrug shoulders and ‘walk on by’ when something ‘odd’ pops up. We should of course take photographs, record the location and email the local BSBI Recorder. There may be many more sites where Symphytum x hidcotense remains undiscovered.

Notes

¹The identity of the parents is not certain. In Stace’s flora, a question mark is added. Some say that Symphytum officinale is a parent. The name Hidcote refers to Hidcote Manor Garden in the Cotswolds, Gloucestershire, where the plant was originally found as a hybrid.

²Students of genetics will understand why this is so – it involves the way chromosomes undergo pairing in meiosis.

³Of course, it may have happened far more times than those reported.

References consulted

Hobbs RJ and Huenneke LF (1992) Disturbance, Diversity, and Invasion: Implications for Conservation. Conservation Biology, 6: 324-337. https://doi.org/10.1046/j.1523-1739.1992.06030324.x   

Johnson N (2008) Hybrid incompatibility and speciation. Nature Education 1(1):20

Lowe AJ, Abbott RJ. (2003) A new British species, Senecio eboracensis (Asteraceae), another hybrid derivative of S. vulgaris L. and S. squalidus L. Watsonia. 24:375–388.

Milne RI (2025) Abbott’s conundrum: why did half of all known recently formed hybrid species arise in the British Isles? Plant Ecology & Diversity, 18(3–4), 125–139. https://doi.org/10.1080/17550874.2025.2583940

Sanders H (2025) Hybrid fertility and the rarity of homoploid hybrid speciation. AoB Plants. 2025 Jun 26;17(4):plaf035. doi: 10.1093/aobpla/plaf035. PMID: 40677589; PMCID: PMC12269824.

Stace CA, Preston CD Pearman DA (2015) Hybrid Flora of the British Isles. BSBI.

Stewart F and Grace J (1984) An experimental study of hybridization between Heracleum mantegazzianum Somm. & Levier and H. sphondylium L. subsp. sphondylium (Umbelliferae). Watsonia, 15, 73-83.

Vallejo-Marín M. (2012) Mimulus peregrinus (Phrymaceae): a new British allopolyploid species. PhytoKeys. 141–14. https://doi.org/10.3897/phytokeys.14.3305

©John Grace