Painting by Otto Wilhelm Thomé (1840–1925), German botanist and botanical artist. In his time the species Arctium minus was called Lappa minor. Image: Public domain, via Wikimedia Commons.
As kids, well before the era of Coke and Pepsi, and decades before Irn-Bru, we drank ‘Dandelion and Burdock’. You can still buy it, in rather over-priced glass bottles with elegant labels, and it is still a very good drink. Or you can make it from the roots of burdock and dandelions – there are recipes on-line (would-be home brewers beware, it is an offence to uproot wild plants without permission from the land-owner!).
Fully grown plant, late July 2022, Bennane Head, Ayrshire. Photo: John Grace.
This week we’ll consider the most common of the Burdock species, Arctium minus, the Lesser Burdock. Fully grown, it is a substantial plant 20-200 cm tall with large basal leaves that are reminiscent of rhubarb and butterbur. Its thistle-like inflorescences with red-purple florets attract bees and large flies, and its hooked floral bracts ensure that any furry animals brushing against the plant will aid dispersal. These hooks were the inspiration for Velcro; the history of that invention, according to Wikipedia, is this:
“Swiss electrical engineer George de Mestral invented his first touch fastener when, in 1941, he went for a walk in the Alps and wondered why burdock seeds clung to his woollen socks and coat, and also to his dog Milka. He discovered it could be turned into something useful. He patented an invention based on tiny hooks in 1955, and subsequently refined and developed its practical manufacture; commercial introduction as Velcro was in the late 1950s”.
Terminal inflorescences, often visited by bees. Photo: John Grace.
It is a native plant, and a biennial (i.e. it can produce its seeds after two years of growth in favourable conditions). In its first year it produces large leaves and makes an overwintering rosette and a stout tap-root. Then, in its second year the fully-charged ‘battery’ of carbohydrates stored in the tap-root enables it to manufacture flower stalks. But, as with many biennials, it often takes a bit longer than two years to complete its life cycle. Once it has flowered, it dies.
Detail of the hooks, which are the modified bracts (‘phyllaries’), sharply hooked and often with yellow tips. The ‘cobwebby’ appearance is referred to as arachnoid. Many species have arachnoid hairs like this, spanning the space between developing organs, although their exact function is not really known. Photo: Chris Jeffree.
It belongs to the Asteraceae, the family formerly called the Compositae, containing the familiar daisy-like flowers (e.g. asters, thistles). The Asteraceae is a relatively modern family, appearing in the fossil record during the Oligocene (33.9 million to 23 million years ago) and Miocene (23 to 5 million years ago). The ancient families such as the buttercups (Ranunculaceae) evolved much earlier (in the Cretaceous, 145 to 66 million years ago). Not only do the Asteraceae have quite different flowers (many tiny florets are grouped to form the ‘flower’, see the image at the top of this blog), but also they also have a completely different carbohydrate storage compound. Instead of starch (a polymer of glucose) they have inulin, a polymer of fructose. Its possible evolutionary advantages over starch were discussed by Hendry (1987). Dieticians are interested in inulin too, as most humans cannot digest this molecule in their stomachs; however, it is broken down in the lower regions of the gut by microbes, forming ‘wind’ composed mostly of carbon dioxide and methane.
Arctium minus can be found in a variety of habitats. Grime et al. (1987) list these: soil heaps, river banks, roadsides, woodland clearings, wastelands, arable fields. It is absent from wetlands. The site I’ve been watching recently is an abandoned field near the sea, where it grows in association with masses of Common Ragwort (Senecio jacobaea) and Scotch Thistle (Cirsium vulgare). However, it isn’t especially associated with coastal habitats, and it is said to be salt-intolerant. It prefers fertile soil (pH 6 to 8).
Burr stuck to my woollen coat; it took some while to remove all pieces. Photo: John Grace.
It never grows in dense colonies, but occurs as scattered individuals. Arctium has travelled far. It reached North America from Europe with the early English and French colonies and is now well established. The US Department of Agriculture describes it thus: “it is tenacious, and aggressively invades disturbed areas, empty lots, parks, roadsides, prairies, fields and pastures. This plant is on the Federal USDA list of Introduced, Invasive and Noxious Plants and is found across most of North America”. Do our American friends exaggerate (as we ourselves sometimes do, when it comes to alien invasive plants), or is it really such a pest? Perhaps North American readers will post a reply. There are many publications on the species from that continent including a most thorough description of the species in the Canadian Journal of Plant Science (Gross et al. 1980): https://cdnsciencepub.com/doi/pdf/10.4141/cjps80-089?download=true
The Canadian authors Gross et al. 1980 are less harsh on its danger as a weed, saying merely: “Although A. minus and A. Iappa are both considered unsightly weeds, only A. minus occurs frequently enough to be a serious pest. Neither species is a serious weed in crops since they are controlled by cultivation”. I did however find several reports of humming birds being destroyed by entanglement in the barbs.
Global distribution of Arctium minus, from GBIF. Note that it has extended far from its native range (Europe), and may have travelled with early European colonists and livestock.
Readers not interested in the taxonomy, should skip this paragraph and simply note that there are other species of burdock. There are two completely different and quite distinct species, the Greater Burdock (A. lappa) and the Woolly Burdock (A. tomentosum). There are two subspecies of A. minus and another species (A. nemorosum) which is so similar to A. minus that many consider it to be merely a subspecies. In fact, Stace (2019) speaks of the uncertain distribution because of confusion between A. minus and A. nemorosum. Many recorders have lumped the two together, treating A. minus as an aggregate. It seems that A. nemorosum is more associated with open woodlands and more northern in its distribution; the maps (below) suggest that A. nemorosum may be rather frequent in Scotland (but I am a ‘lumper’ rather than a ‘splitter’ and I haven’t yet taught myself how to tell the difference). The key in Stace (2019) enables the two species to be differentiated: it requires careful measurements of capitula and the width of those spiny bracts.
British and Irish distribution of Arctium minus (sensu stricto) on the left and A. nemorosum on the right. Note that A. nemorosum is recorded in some places where A. minus is absent, particularly in the NE and the Northern Isles. Data from the BSBI Maps website. Downloaded July 2022.
The web site Plants for the Future is enthusiastic about Burdock, stating that it is one of the foremost detoxifying herbs in both Chinese and Western herbal medicine. There is a long list of its medicinal properties (on which I am not qualified to comment). Likewise, Culpeper’s Complete Herbal of 1653 devotes almost a page to it. I cannot support many of Culpeper’s statements, for example “the juice..given to drink with old wine, doth wonderfully help the biting of any serpents” However, many of the modern research papers I found on the Web of Science are about the identification of active compounds in the leaves and roots, and I am left not doubting the widely proclaimed view that Burdock is a valuable herb.
As for its culinary properties, the roots and young flower stalks are widely used in dishes all over SE Asia. I haven’t (knowingly) tried it but I was interested in this comment (again from Wikipedia): “Burdock root is very crisp and has a sweet, mild, or pungent flavour with a little muddy harshness”. Wildfooduk.com gives this advice “You need to forage the roots in Autumn or Spring of the first year’s growth to be of any worth. The roots can be roasted like parsnip, sliced finely and stir fried or made into a puree. The stems of the younger plants can be eaten until about May when they become woody and bitter”.
There are also folk traditions. In South Queensferry there is an annual event: someone is dressed as the Burryman. Each year he is covered from head to toe with burrs and he parades the town all day. The origin of this very strange custom is lost in the mists of time, but if you are interested you can read the theories and view an astonishing image at https://en.wikipedia.org/wiki/The_Burryman. There has never been a Burrywoman.
References
Grime JP, Hodgson JG and Hunt R (1988) Comparative Plant Ecology. Unwin Hyman.
Gross RS et al. (1980). The biology of Canadian weeds. 38. Arctium minus (Hill) Bernh and A. lappa L. Canadian Journal of Plant Science 60, 621-634.
Hendry G (1987)The ecological significance of fructan in a contemporary flora. The New Phytologist 106, 201-216.
Stace CA (2019) New Flora of the British Isles, 4th Edition. C&A Floristics.
©John Grace
Botany in Scotland 