First thought as two distinct species, the artichoke (Cynara cardunculus L. subsp. scolymus) and the cardoon (Cynara cardunculus L. subsp. cardunculus) vegetables are currently grouped together into a single species along with their wild ancestor (Cynara cardunculus L. subsp. sylvestris). Though the taxonomical debate was no way easy (just like it was for the origin of Potato).
This species is originally Mediterranean, though C. cardunculus sylvestris now has a wider range and is considered an invasive in the many places it escaped into. It belongs to a rather famous plant family, the Asteraceae, that provided humanity with dramatic bunch of garden flowers, and a few crop species as well (Artichoke and Cardoon of course, but also the Sunflower, the Jerusalem artichoke, and the Lettuce to name a few…).
What’s amazing about those two crops is that they differ in the way their domestication was achieved (1), though in both cases it involved reducing spines in the collected organs:
The artichoke is cultivated for its head (or capitula), and therefore multiplication via cuttings was retained. Vegetative reproduction and pereniality were a clear advantage. Indeed, if you have to keep some flowers to generate seeds for the next generation, this is a loss for your production. For the very same reason, the artichoke usually flowers two times a year, in autumn and spring, allowing for two harvests.
(Images from Wikipedia, please click on the picture to have complete attribution)
The cardoon, on the other hand, is cultivated for its stems (well, at least, for there are many possible uses actually). Flowers are thus only interesting to seed production, but investment of resource into leaves and stems is prefered over flowering and maturing seeds, therefore this crop flowers only once, in spring. There was also selection for bigger leaves.
Fair morphological and life-habit differences. A rather good illustration as to how strong selection during domestication can go. But the ancestral species is also morphologically diverse, highly plastic, and is able to grow in a fair number of habitats. This is the reason for its current invasiveness status of course, but may also be the reason why the two vegetables were selected from its gene pool and not from other related species (2), even though wild related species are occasionnally harvested as food, especially in Sicily and South Italy (3). Apparently, not a single time did these wild relatives give birth to an actual crop species…
Interestingly, these domestication events took places at different time, the artichoke was created first and is more ancient. It apparently originated in Italy (4), though it’s historically been travelling around the Mediterranean Basin and was reintroduced during Arabian expansions in Spain as it was adopted as a precious vegetable (1). On the other hand, cardoon seems to have originated more recently, from the western wild cardoon gene pool despite a strong cultural habit of consumption in the eastern range of the species (4). Does all of this have something to do with gardening, I don’t know. There are probably many interesting things to work out about the cultural aspect of this culture!
(1)- G. Sonnante, D. Pignone and K. Hammer (2007).The Domestication of Artichoke and Cardoon: From Roman Times to the Genomic Age. Annals of Botany 100: 1095–1100.
(2)- G. Sonnante, A. V. Carluccio, R. Vilatersana and D. Pignone (2007). On the origin of artichoke and cardoon from the Cynara gene pool as revealed by rDNA sequence variation. Genetic Resources and Crop Evolution 54:483–495.
(3)- D. Pignone and G. Sonnante (2004). Wild artichokes of south Italy: did the story begin here? Genetic Resources and Crop Evolution 51: 577–580.
(4)- G. Sonnante, A. V. Carluccio, A. De Paolis and D. Pignone (2008). Identification of artichoke SSR markers: molecular variation and patterns of diversity in genetically cohesive taxa and wild allies. Genetic Resources and Crop Evolution (online first).