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Wood Burdock

Arctium nemorosum

  • Name also: Woodland Burdock
  • Family: Daisy Family – Compositae, subfamily Carduoideae
    (formerly Aster Family – Asteraceae)
  • Growing form: Biennial herb. Strong taproot.
  • Height: 100–250 cm (40–100 in.). Stem branched, rough, shortly haired.
  • Flower: Flowers form 3–4.5 cm (1.2–1.8 in.) wide, single flower-like capitula surrounded by involucral bracts. Capitula lack ray-florets, disk florets purple–red, tubular. Stamens 5. Gynoecium composed of 2 fused carpels. Involucre virtually spherical, woolly when young, becoming glabrous. Involucral bracts overlap in many rows, long, straggly, narrowly elliptic, rigid, green–red dots, usually red–yellow tips. Capitula corymbose–racemose groups, branches curving, pedicel 1–2 cm (0.4–0.8 in.) long.
  • Leaves: Alternate, stalked. Blade broadly ovate, cordate based, small-toothed, underside white-greynish-cottony.
  • Fruit: Flattish, clearly curved, light grey-brown, dark-spotted, 6–9 mm (0.24–0.36 in.) long achene with short yellow hooked hairs on tip.
  • Habitat: Broad-leaved forests, forest glades, coppices, waterside alder thickets, sometimes by roadsides.
  • Flowering time: July–September.
  • Endangerment: Endangered.

Most Finnish burdock species are more or less dependent on human activity, but wood burdock grows completely in the wild in sunny hazel woods and rich coastal alder groves. The species has a narrow band of distribution in Finland, from the south-west archipelago to Houtskari on the south-west tip of mainland Finland. On the mainland its usual stands have decreased, becoming very small or non-existent. Wood burdock can stand shade better than our other burdocks, but the main threats still come from being hemmed in by fir trees and being otherwise crowded out. The end of forest grazing and wooded meadows has cast a grave shadow over the future prospects of the species in many areas. It has been verified that wood burdock can spread from natural forest glades to roadsides that run through them, sometimes even to gardens and field margins. The species’ strongest foothold on the mainland is probably around the centre of Houtskari. Almost all forest glade stands in Finland are very small, composed of only a few plants. Burdocks are mainly self-pollinating, so the plant can spread in this way. Individual plants are not however long-lived: they grow a rosette for a year or sometimes two before they flower and then die.

Wood burdock resembles tall-growing lesser burdock: both capitula are arranged in the same fashion in racemose clusters rather than an even-topped corymb. Wood burdock’s inflorescence branches curve downwards however, rather than rigidly spreading like lesser burdock. Wood burdock’s involucre is also larger than average and egg-shaped. The individual florets of the capitulum are roughly the same length as the involucral bracts, while on lesser burdock they are longer. Both species’ internal variation and cross-breeding make identification more difficult, and sometimes they are regarded as subspecies of the same species. Wood burdock’s natural habitats do not however include other burdocks, which would blur the boundaries between the species.

Other species from the same genus
Other species from the same family

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