Arctium lappa [Greater Burdock]

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Rørslett, B. 2014. Arctium lappa L. (Asteraceae). Greater Burdock. Flowers photographed in visible and ultraviolet light. http://www.ultravioletphotography.com/content/index.php?/topic/907-arctium-lappa-greater-burdock/

 

Arctium lappa L.

Syn. Lappa major Gaertn.; Lappa officinalis All.

NO: Storborre

SE: Stor kardborre

DK: Glat Burre

FI: Isotakiainen

DE: Große Klette

EN: Greater Burdock

 

This species, native to Europe and introduced elsewhere, can grow to a huge size (2-2.5 m or more), and carry densely packed flower heads arranged in flat-topped corymbs towards the tip of the branches. Burdocks prefer rich deep soils and like some shade, although they do occur plentiful on fallow fields, road edges, or wastelands. Perhaps damp, fertile and open deciduous forests or riparian locations are their native habitats.

 

Basal foliage is massively sized, but stem leaves tend to be much smaller. Each capitulum (flower head) is 3-4 cm across and carries stiff, spine-like phyllaries with tips shaped as sharp hooks. The capitulum breaks off and clings to any animal coming by. This is a text-book example of epizoochori. The flower heads are very eagerly visited by a wide range of pollinators.

 

Although mainly considered these days as an annoying and troublesome weed, A. lappa has had extensive use in folk medicine, and sometimes is cultivated for its foliage and tap roots. The English 'Dandelion and Burdock' drink is but one example of its non-weedy usage.

 

Not surprisingly given their size and prickly stature, any of the handful of Arctium species is little studied and their representation in herbaria is scattered at best. To exacerbate the situation, all species hybridise freely and hybrids probably are much more common than mentioned in the literature. Thus, the four species acknowledged in Europe (A. lappa, A. nemorosum, A. tomentosum, A. minus) can be quite difficult to identify with certainty in the field. Specimens with large flower heads (> 3 cm across) and phyllaries extending at least 10 mm are either A. lappa or A. nemorosum, or hybrids in which one of them occurs. Most of the material I have studied in field (around Oslo, Norway) is A. tomentosum (or its hybrids), with much more occasional observations of A. lappa or A. minus. A. nemorosum appears to be very rare in this region. I plan on presenting all of the burdock species here on this site.

 

Material for the current topic represents typical A. lappa and was collected at Blindern, Oslo, Norway 14 July 2014. To underscore its low frequency, only 1 out of 100 burdock specimens here could be referred to as A. lappa. The capitula measured 3.5-4 cm and the hairless green spines extended around 12 mm on the studied plant.

 

Image reference: ARCT_LAP_B407144982_VIS.jpg

Visible light: Nikon Df, Voigtländer APO-Lanthar 125 mm f/2.5 lens, daylight.

 

Image reference: ARCT_LAP_I1407142028_UV.jpg

Ultraviolet light: Nikon D3200 (modified), UV-Nikkor 105 mm f/4.5 lens, internal Baader U2" (Venus) filter, SB-140 flash.

 

The anther tubes are UV-dark, as so often seen in the Asteraceae. The corolla and stigmas are quite UV bright. There is an indication that the spiny phyllaries contribute to the overall UV signature by being quite shiny under UV light.

 

[ Published 17 July 2014 ]