Heracleum mantegazzianum

H. mantegazzianum is a monocarpic perennial herb, growing from a yellow, branched root system 40-60 cm deep and up to 15 cm across at the crown when mature. The root is somewhat contractile pulling the crown down to about 10 cm below the soil surface. While still vegetative, there is a rosette of leaves, increasing in size each year. These are alternate, the lowermost eventually up to 3 m long, to 1.7 m broad, ternately or pinnately lobed and coarsely toothed. Upper leaves on the flowering stem are progressively smaller. The upper leaf surface is glabrous but the underside and petiole are covered in bristles. When it finally flowers, usually after 3-5 years, there is a single hollow stem up to 2-5 m high and 10 cm in diameter. The stem is ridged, with purple blotches, and covered in pustulate bristles. The main inflorescence is a terminal compound umbel up to 80 cm across with about 100 unequal hairy rays, each 10-40 cm long. There are also up to eight satellite umbels which overtop the main one, and others developing on branches below. The main umbel is hermaphrodite;the lower ones, maturing earlier, may be only male. Flowers, on pedicels 10-20 mm long, are white or pinkish with petals up to 12 mm long. Numerous fruit flattened, elliptical, 6-18 mm long by 4-10 mm wide, narrowly winged, the larger fruits occurring on the main inflorescence and the smaller on satellites;glabrous to villous, splitting into two mericarps, each with 3-5 elongated oil ducts. For the first few years, the above-ground growth dies down each winter. Once it has flowered, the plant dies altogether (from Tiley et al., 1996.) Nielsen et al. (2005) have excellent line drawings of H. mantegazzianum and related species.