This section is from the book "British Wild Flowers - In Their Natural Haunts Vol2-4", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
With its characteristic and conspicuous seeds it is not surprising that the Cow Parsnip has been found in Interglacial beds at Pakefield, Suffolk, and in Late Glacial beds at Twickenham, Middlesex; limited to the North Temperate Zone, it is found in Europe, North Africa, and N. Asia. Hogweed (another name for this plant) is very common, and found in every part of Great Britain, in the Highlands ascending to 2700 ft.
Hogweed is one of those common wayside plants that help to enable one to picture the flora of a roadside ditch, for there is probably not a road in the kingdom where there are boundary hedges where this very ubiquitous species does not grow. It is fond of securing for itself the ample shelter and space of a shelving ditch where it receives moisture and good light, and where rich loam affords a suitable subsoil for it. So tall and handsome a plant cannot escape notice by the wayside. The stem is tall, hollow, furrowed, and hairy.
The second Greek name, meaning vertebra, refers to its jointed character. The leaves are large, triangular, with lobes on either side of a common stalk, very much divided, usually into 5 segments, oblong, with acute teeth. They are broadly sheathed at the base, and in the bud the sheaths form a conical cap over the young plant.
Not the least conspicuous part of this wild flower is the wide umbel of the flower. The umbel contains general and partial involucres or whorls of leaflike organs with many rays. It is generally flat, and the flowers are large, white, or pink, with notched petals, with bent-in points, and the outer florets are in a ray. The fruit is nearly round, with a short style, and with a notch.
Hogweed is sometimes 10 ft. high, but more usually 4 to 6. It blooms in May and June. It is a deciduous, herbaceous plant, propagated by division.
The flowers are often polygamous, and the outer ones are rayed, the whole umbel large and conspicuous. In some cases there are only hermaphrodite flowers, elsewhere the partial umbels have male flowers only at the ray, the other umbels being male throughout, or perhaps female. The plant has a strong, but not altogether pleasant smell. The petals are bent inwards. The styles are short. It is visited by numerous insects, so that cross-pollination is the usual thing. The visitors are numerous, Diptera, Coleoptera, Hymenoptera, and Hemip-terous insects, as many as 118 having been observed.
Inset Photo. Matson