Wetland Umbellifers
What are they?
Members of the umbellifer family (Apiaceae) are a familiar sight in the countryside and a number of species favour wetland locations. Most members of this family are immediately recognisable by their distinctive flowerheads, which consist of multiple rays spreading out from a single point on the stem, with these rays then bearing a further set of shorter rays at their tips; the flowers are carried singly at the ends of these secondary rays and the flowers are followed by distinctive fruits. Some members of this family are small annuals, while others are large biennials, forming a leaf rosette in the first year then flowering and fruiting in the following year. Some are longer-lived perennials. This is a rather unusual family since it contains plants that are commonly grown as vegetables or culinary herbs, as well as some dangerously poisonous ones - so correct identification can at times be vital!
Where are they found?
This page deals specifically with umbellifers that are found in wetland habitats, including permanently wet sites such as rivers, streams and ponds, as well as ditches, hollows and scrapes that may only be seasonally wet (typically in the winter and/or spring). Despite all being wetland plants, some are rather specific in their habitat choice, so the wetland type can be useful in helping to identify the plant.
Identification
Umbellifers may seem rather daunting at first as they all can look rather similar. However, the secret is to use a combination of characters to arrive at the correct identification. Features to check should include flower colour, stem detail (spotted/hairy/ridged), leaf detail (especially fineness of the leaf segments), fruit/seed capsule detail (shape and hairiness or whether grooved on the surface) and a check for the presence or absence of bracts or bracteoles at the points where the flowerhead rays meet (bracts at the lower, main node and bracteoles at the upper node, just below the flowers). Where possible, all these features are shown in the photos below and bract/bracteole locations are shown even when these features are absent - which can be a useful feature. Flowerheads of the water-dropworts are rather distinctive, with each group of flowers at the end of each terminal branch forming distinct, rounded clusters. Note also that many species have distinctive scents, so sniffing the plant can be useful and is best achieved by squeezing and rubbing part of the leaf or stem or digging in a thumb nail to help to release the scent.
Common Celery Apium graveolens
Native. Mostly a coastal species, occurring in reedbeds and along wet ditches and dykes in coastal areas and low-lying areas in the Fens and lower Broads. The ancestor of the culinary celery that we eat. Flowers June to August. Petals white but often with a greenish or yellowish tinge. Leaves once-pinnate, leaflets relatively broad and strongly toothed at the margins, hairless; bracts and bracteoles usually absent; fruits rounded, laterally compressed and strongly ribbed. Gives off a strong celery scent.
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Fool's Water-cress Helosciadium nodiflorum
Native. Widespread and often abundant in muddy ditches, pond edges and other areas of slow-moving and static water, often filling narrow channels with extensive mats of foliage. Flowers July to August. Petals white but often with a greenish or yellowish tinge. Leaves once-pinnate, finely toothed at the margins, hairless; bracts usually absent but sometimes 1-2 and bracteoles usually absent but sometimes up to seven, typically relatively broad and with paler margins; fruits rounded, laterally compressed and strongly ribbed. Flower clusters usually appear on short branches along the stems and opposite the leaves. A very variable plant that may be small and creeping in seasonally dry, open sites, or upright in wetter sites and when growing amongst other, tall plants.
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Hybrid Fool's Water-cress Helosciadium x moorei
Native. A very rare hybrid between Fool's Water-cress and Lesser Marshwort; currently known to occur in a couple of sites in the Norfolk Broads. Flowers July to August. A small plant, found in wet ditches and shallow channels and having leaves that are intermediate between the parents, being once-pinnate but often quite deeply lobed. It appears to be sterile and does not form fruits.
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Lesser Marshwort Helosciadium inundatum
Native. Rare and only recorded in a handful of locations, scattered throughout the East Anglian region in species-rich wetlands. Flowers June to August. Petals white. Leaves twice-pinnate with narrow segments, especially on submerged leaves, hairless; bracts usually absent; bracteoles 3-6; fruits rounded, laterally compressed and strongly ribbed. Flower clusters usually appear on short branches along the stems and opposite the leaves. A tiny, creeping plant.
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Creeping Marshwort Helosciadium repens
Native. Extremely rare in the UK, this species was found at Thetford in 2020 and is currently only known to occur at one other site in the country, in Oxfordshire - thus its discovery here was wholly unexpected. Flowers June to September. Petals white. Leaves once-pinnate with broad segments, hairless; bracts 4-7; bracteoles 4-7; fruits rounded, laterally compressed and strongly ribbed. A low, creeping perennial that roots at the nodes.
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Lesser Water-parsnip Berula erecta
Native. Widespread and common in a wide range of wetland habitats, often mixed in with Fool's Water-cress. Flowers July to September. Petals white. Leaves once-pinnate, usually coarsely toothed at the margins with the leaflets turned at 90 degrees to the main axis, hairless; bracts 4-7; bracteoles 4-7; fruits rounded, smooth and shiny. Flower clusters usually appear on short branches along the stems and opposite the leaves. Easily confused with Fool's Water-cress and most easily told from it by a ring-mark on the leaf stalk.
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Greater Water-parsnip Sium latifolium
Native. Very rare at a handful of locations in the region generally, but locally frequent in the Broadland region of Norfolk, especially along the wetlands of the Ant and the Bure. Flowers July to August. Petals white. Leaves once-pinnate, usually regularly toothed at the margins with the leaflets turned at 90 degrees to the main axis, hairless; bracts 2-6; bracteoles 3-6; fruits eliptical, laterally compressed. A taller plant than Lesser Water-parsnip and with the flower clusters at the ends of the branches.
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Fine-leaved Water-dropwort Oenanthe aquatica
Native. Scattered throughout the region and usually growing in shallow ponds with muddy bottoms, often those that dry out in summer. Generally uncommon but sometimes grows in great quantity in suitable habitat and can carpet a pond, such as in the pingos of the Norfolk Brecks. Flowers June to September. Leaves three- to four-pinnate, the leaf segments very narrow and mostly obviously so on submerged leaves, hairless; bracts absent, bracteoles 4-8; fruits oval or almost egg-shaped.
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River Water-dropwort Oenanthe fluviatilis
Native. Scattered throughout the region and usually growing in the deeper water courses of permanent rivers. Generally uncommon but can be locally common in favoured locations. Flowers July to September. Leaves two-pinnate, the leaf segments relatively broad for a water-dropwort, hairless; bracts absent, bracteoles 4-8; fruits narrowly oval or cylindrical in outline. This fairly stout species almost always grow submerged in permanent water and can be hard to spot until the flowering stems appear in mid to late summer.
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Tubular Water-dropwort Oenanthe fistulosa
Native. Scattered throughout the region in a range of wetland habitats from ditch sides and wet river banks to wet fens and fen meadows but usually avoiding more brackish or salty habitats. Flowers July to September. Lower leaves three-pinnate, upper leaves once-pinnate, hairless; bracts absent, bracteoles 7-16 and typically rather short; fruits oval or cylindrical, typically broader at the top, each with two, persistent styles at the top which often give a spikey look to developing fruits. The upper stems and upper leaves are thin-walled and have large, central spaces that produce a distinctive, tubular effect.
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Parsley Water-dropwort Oenanthe lachenalii
Native. Mostly found in brackish wet meadows and other damp habitats towards the coast, but also at one or two good-quality fens inland. Flowers June to September. Lower leaves usually two-pinnate, upper leaves one- to two-pinnate with very narrow, linear segments, hairless; bracts 0-5, bracteoles 5-7 and typically rather short; fruits oval or cylindrical, with narrow ridges. The stems and leaf stalks are solid, not thin-walled and tubular.
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Hemlock Water-dropwort Oenanthe crocata
Native. Rather rare in East Anglia but known from a wide scattering of sites in muddy wetlands, wet woods and ditch banks and may be increasing in the region. Flowers June to July. Lower leaves three- to four-pinnate, often present as a basal rosette over winter and easily mistaken for the leaves of Common Celery. Upper leaves one- to two-pinnate with narrower segments than the lower leaves, hairless; bracts 4-6, bracteoles 6-10; fruits cylindrical with narrow ridges. A taller growing, perennial species that should be handled with care as all of its parts are extremely poisonous.
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Corky-fruited Water-dropwort Oenanthe pimpinelloides
Native. Very rare in coastal grassland and currently only known from a single location in our region, on the outskirts of Ipswich, where it forms an extensive colony in rather dry, rank grassland beside Belstead Brook. Flowers June to August. Lower leaves usually two-pinnate, upper leaves one- to two-pinnate with very narrow, linear segments, hairless; bracts 0-5, bracteoles 12-20 and typically very narrow; fruits oval or cylindrical, with prominent ridges, their stalks thickening as the fruits mature. The stems and leaf stalks are solid, not thin-walled and tubular.
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Common Milk-parsley Peucedanum palustre
(Thysselinum palustre) Native. Found in a few tall-herb fens scattered across the region but locally common in good quality fens and reedbeds in Broadland, where it is the food plant for the larvae of the British race of Common Swallowtail butterfly. Flowers July to September. Lower leaves usually two- to four-pinnate, upper leaves one- to two-pinnate, hairless; bracts 4-6, bracteoles 5-10 and typically rather long and pale-edged; fruits elliptical, flattened laterally. Unlike the water-dropworts that are found in similar habitats, the flowers merge together to form a larger, flatter head.
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Cambridge Milk-parsley Selinum carvifolia
Native. Very rare with its entire UK population being confined to three wet fen reserves in Cambridgeshire. Flowers July to October. Leaves usually two- to three-pinnate, hairless; bracts 1-2 but soon falling, bracteoles 8-10; fruits elliptical, strongly flattened dorsally and with large, lateral wings.
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Common Cowbane Cicuta virosa
Native. A Nationally Scarce species with a British stronghold in the East Anglian Broads region, where it occurs along the edges of dykes, ditches and in tall fen vegetation. Flowers July to August. Leaves two- to three-pinnate with long, fingered segments that are deeply toothed, hairless; bracts absent, bracteoles numerous; fruits globular, slightly flattened laterally. The long-fingered, coarsely-toothed leaves are the easiest feature to use to identify this species.
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Common Angelica Angelica sylvestris
Native. A common and widespread species, found in a wide range of riverside and wet meadow habitats as well as in damp woodland. Flowers July to September. Leaves two- to three-pinnate with coarse, broad segments that have toothed margins, lightly hairy; bracts 0-3, bracteoles 6-10, narrowly linear; fruits oval, strongly flattened laterally and with clear ridges and broad wings. The leaf stalks are strongly inflated at the base and the inflated bases of the upper leaves surround the newly emerging flowerheads. The stems are often purple-tinged and have a downy covering of short hairs.
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Hemlock Conium maculatum
Native. A very common and widespread species, typically found in greatest abundance along the margins of channels and ditches in the Fens, but also common in drier, disturbed habitats and as a weed of hedgerows and field margins on nutrient-rich soil. Flowers June to July. Leaves two- to four-pinnate with fine 'ferny' segments, hairless; bracts 5-6, bracteoles 3-6; fruits globular with bumpy ridges. Despite being only an annual or biennial, plants may grow to 2.5m in height and often form dense colonies. Plants smell very strongly and distinctively of male mice; stems strongly purple-spotted and the whole plant is highly poisonous.
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Giant Hogweed Heracleum mantegazzianum
Introduced. A potentially highly invasive species that grows at odd sites scattered throughout the region, most often in damp ground close to rivers or lakes. Flowers June to September. Stems massive, to five metres in height, with flowerheads like great cartwheels, bearing 40-50 rays. Lower leaves enormous, to 75cm x 65cm in size one- to two-pinnate, lightly hairy; fruits oval and strongly flattened, hairy and with four dark, linear glands that are thickest at the base. A controversial plant due to its invasive nature and its potent sap that can produce rupturing blisters if it gets into contact with the skin, especially during hot weather.
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