īorscht is a sour soup common in Eastern Europe and Northern Asia. The seed dispersal is by wind (anemochory). The small fruits are schizocarps, flattened and winged, elliptical to rounded and glabrous, and up to 1 cm long. The flowers are pollinated by insects, such as beetles, wasps, and especially flies. This may result from the over-production of flowers that, due to limited plant resources, never set seed. Most plants show facultative early abortion of carpels. The earliest flowers to open (i.e., those on the primary umbel) are the most likely to set seed.
Geitonogamy is permitted, however, as filament length is relatively long. Anthesis precedes stigma receptivity within any flower by approximately 8–10 days. Self-pollination may occur, but the andromonoecious flowers are protandrous, tending to limit this. The flowering is phased within the umbel, with the outer row of larger flowers on each umbellet opening first. Flowering occurs between June and October. The terminal umbels are flat-topped, and the outermost petals are enlarged. The peripheral flowers have a radial symmetry (zygomorphic). Hogweed has five-petalled pinkish or white flowers arranged in umbels, usually less than 30 cm in diameter, with 15 to 30 rays. The leaves are lobed and pinnate with small, serrated segments ( Figure 3C). Table 1 reports the classification of common hogweed habitats according to the CORINE biotopes classification. Its most common habitat is that of meadows and woods, especially in mountainous areas up to 2500 m, and is an indicator of soils rich in nitrogen.
In northern Europe, the distribution of this species may be limited by low temperatures, soil fertility, and pollination requirements. The Mediterranean region represents the southern limit to the distribution of this species, probably because the minimum winter temperatures are too high for the after-ripening requirements of the seeds ( Section 7), and the extended drought periods affect seedling survival. Throughout Europe, the distribution is broadly within mean annual temperatures of 5–15 ☌ and mean annual precipitation of 700–5000 mm. The species has also been introduced to suitable habitats elsewhere, such as in North America. sphondylium is a plant with distribution in Europe south of 61° latitude, including Great Britain, up to north-western Africa, and both western and northern Asia.
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