Plant of the Week – 9th August 2021 – Carrots – Daucus carota subspecies carota, sativus and gummifer.

Daucus carota L. is a member of the Apiaceae (Umbelliferae) with three subspecies in the UK. (We have previously blogged about four other members of the Apiaceae – the ‘very poisonous’ Hemlock Water Dropwort (Oenanthe crocata), the ‘avoid touching’ Giant Hogweed (Heracleum mantegazzianum) , the ‘some people eat it but be certain of your identification’ Hogweed, (Heracleum sphondylium ssp. sphondylium) and Wild Angelica (Angelica sylvestris), which has various herbal uses). You can find all these previous blogs at https://botsocscot.wordpress.com/index/.

Species in Britain and Ireland

In this week’s blog, we talk about the subspecies of Daucus carota which occur in the UK – the two wild subspecies carota and gummifer, and the subspecies sativus, which is a globally important food crop and the domesticated descendant of subspecies carota – (‘sativus‘ means cultivated, which makes it easier to remember which are which).

A meadow of Wild Carrot –Daucus carota subsp. carota, at Portrack Marsh Nature Reserve, Stockton on Tees © Chris Jeffree
Wild Carrot Daucus carota subsp. carota growing in dunes at Ballantrae, Ayrshire © John Grace

The inflorescence of D. carota is typical of many Apiaceae, with a compound umbel (a botanical term dating from the 1590s derived from the Latin umbella “parasol, sunshade,” diminutive of umbra “shade, shadow” www.etymonline.com/word/umbel), composed of many white ‘umbellets’ with the central umbellet often but not always reduced to a single protruding maroon floret. Members of the genus Daucus are particularly decorative because of their numerous finely divided bracts which frame the umbel. After anthesis, the umbel closes tightly, and seed dispersal begins as the umbel dries. Dispersal can take many months, and the dead umbel responds to changes in atmospheric humidity by hygroscopic movement, bending towards the axis of the main umbel when the air is humid, and away from the axis when humidity decreases (Lacey, 1980).

Young inflorescence Daucus carota subsp. carota, surrounded by decorative bracts © Chris Jeffree
Open umbel of Daucus carota subsp. carota © Chris Jeffree
Maturing seedhead of Daucus carota subsp. carota, showing the closed umbel © Chris Jeffree

One of the features of Daucus carota (and some other Apiaceae) is the frequent occurrence of a dark maroon floret in the middle of the umbel, and there have been many investigations and discussion as to its significance. Charles Darwin (1877) disagreed with suggestions that it attracted insects and thereby helped pollination and considered that it was simply a remnant of previous species from which it had evolved, in which only the central flower was female. However, many researchers have continued the quest to understand its significance but results are still equivocal and the debate continues (Polte and Reinhold, 2013).

According to Stace (2019), Daucus carota has three subspecies in Britain and Ireland– subsp. carota (Wild Carrot, Queen Anne’s Lace), subsp. sativus (Carrot) and subsp. gummifer (Sea Carrot). The two former subspecies are widespread, while subsp. gummifer is much more local, and mostly coastal from Anglesey to Kent, although the BSBI* lists occasional records of gummifer from the West of Scotland (mostly before 1986, but one record from 1997 on Coll and two from 2009 from Rum). Subsp. carota is mostly coastal too in Scotland. The carota and gummifer subspecies are both native, while sativus is a ‘neophyte-survivor’ (an alien species which arrived after 1500, which has not naturalised, but persists as a relic of planting. They are all mostly biennial, flowering in their second year.

I have never seen subsp. gummifer, but Stace (2019) tells us that the umbels are convex to slightly concave when in fruit, whereas those of sativus and carota are both very contracted when in fruit and very concave.

Sea Carrot (Daucus carota var. gummifer on Anglesey. Photo by Steve Povey CC BY-SA 2.0 https://commons.wikimedia.org/wiki/File:Sea_Carrot_at_South_Stack,Anglesey.geograph.org.uk-_1279145.jpg

Subspecies gummifer is very rare in Scotland, where it reaches its northern limit of distribution. In the British Isles it mostly occurs on coastal fringes in southern England and Ireland and Wales. GBIF maps show that it is most frequent along the Atlantic coasts of Spain and Portugal.

Daucus carota subsp. sativus is the edible carrot which we grow in our gardens and regularly eat. It is thought to be the domesticated relative of subsp. carota. Reflecting their domestication, roots of subsp. sativus are swollen in the first year and usually orange, and leaves are bright green, whereas those of undomesticated carota are not swollen, fibrous, whitish and the leaves are grey-green.

Domestication

The cultivated carrot (subsp. sativus) is an important global food crop, nutritious and stores well. 100g of carrot provides more than the recommended daily intake of vitamin A.

Wild carrot has a wide native range, from temperate Asia, through the Indian subcontinent, Europe and Northern Africa (GBIF) and is the progenitor of the cultivated carrot.

Daucus carota subsp. carota in GBIF Secretariat (2021). GBIF Backbone Taxonomy. Checklist dataset https://doi.org/10.15468/39omei accessed via GBIF.org on 2021-08-07.

It is thought that the domestication of carrots commenced comparatively late – about 1000 years ago. The wild carrot has a tough, fibrous and unswollen root, and so domestication must have faced many challenges on the way to the carrots which we eat today.

Banga (1957) reviewed ancient literature and could not find any clear references to carrots prior to the 10th Century, although carrot seeds have been found associated with Neolithic and Bronze Age sites – so perhaps seeds were collected for use long before domestication as a root crop occurred. First evidence of the use of carrot roots in Europe appears in the 10th Century, with increasing references thereafter and they are referred to in an English cookery book from the 15th Century. . Early domesticated carrots were yellow or purple (due to anthocyanins) and it is thought that selection for orange colour (due to carotene) occurred much later. Using evidence from literature and art, Banga shows the history of different coloured carrots in Europe and suggests the purple carrot was not always popular because they coloured everything that they were cooked with in the pot.

Iorizzo et al. (2013) compare their results of the genetic structure of the cultivated carrot with observations by various authors based on morphology (eg minimal lateral root development being one of the first indicators of domestication) and historical records, and concluded that wild carrots from Central Asia are the closest relatives to the domesticated carrot. Domesticated Western carrots have higher pro-vitamin A and sugar content than Eastern carrots (Que et al., 2019).

Although the wild carrot is edible, do not try it unless you are absolutely certain of your identification. There are many other species in the Apiaceae which appear similar but are extremely toxic.

The online Carrot Museum www.carrotmuseum.co.uk/ tells you so much more about carrots. I recommend a look.

*BSBI = Botanical Society of Britain and Ireland https://bsbi.org/maps

References

Banga, O. (1957) Origin of the European cultivated carrot and the development of the original European carrot material. Wageningen : IVT, 1957. (Mededeling / Instituut voor de Veredeling van Tuinbouwgewassen; 105). Euphytica 6:54-63, Euphytica 6: 64-76 392193 (wur.nl)

Darwin C. (1877) The different forms of flowers on plants of the same species. John Murray, London. http://darwin-online.org.uk/content/frameset?itemID=F1277&viewtype=text&pageseq=1

GBIF Global Biodiversity Information Facility https://www.gbif.org/species/7224071

Iorizzo M, Senalik DA, Ellison SL, Grzebelus D, Cavagnaro PF, Allender C, Brunet J, Spooner DM, van Deynze A, Simon PW (2013) Genetic structure and domestication of carrot (Daucus carota subsp. sativus ) (Apiaceae). American Journal of Botany 100(5): 930–938.

Lacey EP (1980) The influence of hygroscopic movement on seed dispersal in Daucus carota Apiaceae). Oecologia (Berl.) 47: 110-114.

Polte S. and Reinhold K. (2013) The function of the wild carrot’s dark central floret: attract, guide or deter? Plant Species Biology 28: 81–86.

Que, F., Hou, XL., Wang, GL., Xu ZS, Tan GF, Li T, Wang YH, Khadr A, Xiong AS (2019) Advances in research on the carrot, an important root vegetable in the Apiaceae family. Hortic Res 6, 69 (2019). https://doi.org/10.1038/s41438-019-0150-6

Stace, CA. (2019). New Flora of the British Isles (4th ed.) Middlewood Green, Suffolk: C & M Floristics. ISBN 978-1-5272-2630-2

Julia Wilson

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