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Eupatorium cannabinum

  • Name also: St. John’s Herb, Holy Rope, Hemp Agrimony
  • Family: Daisy Family – Compositae, subfamily Asteroideae
    (formerly Aster Family – Asteraceae)
  • Growing form: Perennial herb.
  • Height: 40–150 cm (15–60 in.). Stem branchless–upper part branching, brownish red, densely haired at least at top.
  • Flower: Single flower-like, approx. 7 mm (0.28 in.) capitula, surrounded by involucral bracts. Capitula’s ray-florets lacking; disc florets (5–6) reddish, tubular. Stamens 5. Pistil of 2 fused carpels. Involucre cylindrical, involucral bracts in 2 rows, round-tipped, with membranous margins, reddish. Capitula a corymbose inflorescence.
  • Leaves: Opposite, short-stalked. Blade 3(–5)-lobed–with leaflets, lobes–leaflets lanceolate, with toothed margins.
  • Fruit: 5-edged, greyish brown–black, approx. 3 mm (0.12 in.) long achene, tip toothed with unbranched hairs.
  • Habitat: Flooded shores, damp broad-leaved forests, stream banks, rich hedgerows.
  • Flowering time: July–September.

Hemp-agrimony is a member of the Daisy family although at first glance its inflorescence might be misleading. Sometime back in the dawn of the evolution of the Daisy family, hemp-agrimony’s forefathers had regular, separate flowers that attracted insects, and then the flowers merged to produce a densely flowered capitula. During its development the capitula bunched up to form a dense umbel, at which point the size of the capitula began to decrease along with the number of flowers. Nowadays hemp-agrimony’s capitula consist of only a few flowers, but some of its relatives have developed in a full circle back to the beginning, with only one flower in each capitula. Human logic has difficulty finding any sense in this, but from the point of view of evolution hemp-agrimony is a success story: it is still around after millions of years, and among nectar plants hemp-agrimony sits at the top table. The inflorescence attracts mainly bees and butterflies, and night butterflies too to a certain extent. Many flower flies and other little insects also like to visit.

Hemp-agrimony grows in several places by the coast, on stream banks and in broad-leaved forests in southern and south-western Finland. The species is so rare in Finland, however, that is has been seldom observed in the wild and not much is known about its existence there. Most Finnish stands have been small or sparse – and nowadays many have unfortunately completely disappeared. For some reason the species has never been able to form established stands in many places even though there would seem to be plenty suitable coastal habitats: Finland is known as the Land of the Thousand Lakes after all. (Actually there are 187,888 lakes in Finland, of which 60,000 are large!)

Hemp-agrimony has sometimes been used medicinally: it has been observed to act as a general tonic and to have blood-cleansing properties. The species is too rare to be collected in Finland and is best left to grow in peace because it can irritate the skin on contact. Hemp-agrimony’s leaves look slightly like hemp’s, as its Latin name also refers to. The plants have nothing else in common, however with regard to kinship or qualities.

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