This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
In spite of its tender character this plant has been found and identified from seeds in Interglacial beds at West Wittering in Sussex. It is found in the North Temperate Zone at the present day in Europe and N. Africa. In this country it is found throughout the Peninsula, Channel, Thames, Anglia, and Severn provinces, except in the last in Monmouth; in Wales only in Glamorgan, Brecon, Carnarvon; Trent provinces; in the Mersey province, except in Mid Lancs; in the Humber, Tyne, and Lakes provinces; and in Dumfries, Kirkcudbright, Ayr, Renfrew, Berwick, Mid Perth, or from Ayr southwards. It is rare in Scotland, but common in Ireland.
Water Dropwort is a hygrophilous or moisture-loving species which is found in most marshes, and in wet places where a marsh may once have existed formerly. It is also found in ditches, and on the borders of rivers, lakes, ponds, and other tracts of water; but most profusely in water meadows, in hollows once (or now) forming part of a marsh.
As the second Latin name denotes, the stem and the leaf-stalks of this plant are fistular or hollow. It is freely stoloniferous, with creeping stems or shoots, and forms extensive beds where it grows for that reason, and being tall and erect they dot the wet meadows in summer over a wide area. The stem leaves have thread-like pinnae. The stalks exceed the leaves in length, these last being 2-3, pinnate, with leaflets divided into three nearly to the base.
Photo. Flatters & Garnett - Water Dropwort (Oenanthe fistulosa, L.)
The plant is 2-3 ft. high, and flowers from July to September. It is perennial, increased by stolons.
As the first Greek name implies, the Water Dropwort (and others) has a smell like wine, which helps to make it attractive to insects. The outer flowers are male, and the plant is polygamous. The petals are inflexed or turned inwards, the styles are long, erect, and armed with points. It is arranged so that insects can cross-pollinate it. The visitors are Stratiomys, Empis livida, E. rustica, Antherix, Syritta pipiens, Eristalis nemorum, E. arbustorum, E. stpulcralis, Lucilia, Trichius fasciatus, Macropis, Heriades. The anthers and stigma ripen together in some flowers which are complete in the centre.
The fruits are flattened, angular, and furrowed, and so the more readily dispersed by the wind, and being but slightly attached are easily detached by it or by passing animals.
A beetle, Lixus paraplecticus, a moth, Depressaria nervosa, and a fly, Simulium reptans, feed upon it.
Oenanthe, Theophrastus, is from the Greek oinos, wine, anthos, flower, and the second Latin name refers to its fistular character. It is called Water Dropwort and Hemlock Dropwort. It is a poisonous plant like Wild Celery, Fool's Parsley, and other umbellifers.
Essential Specific Characters: 128. Oenanthe fistulosa, L. - Root fibrous, slender, with runners, stem hollow, leaves pinnate, shorter than the petioles, which are fistular, the lower ones flat, flowers white at first, pink, in few-rayed umbels, fruit with rigid divergent or spreading styles.