Hydrocotyle vulgaris

Pennywort Family [Hydrocotylaceae]  

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3rd Aug 2006 Photo: © Paul Breslin
Usually short, but 3 inches tall, but can be much shorter or much longer. Grows in shallow water often overgrown by much larger plants.

3rd Aug 2006 Photo: © Paul Breslin
The leaves carpet the ground hiding the wetness beneath and are variable in size from 8-35mm across

8th July 2009, Ainsdale dunes, Southport, Lancs. Photo: © RWD
The leaves are shiny, almost round with less than a dozen shallow lobes on the periphery. Stem in the centre. They are peltate (round) and crenate (with rounded teeth), the stem in the centte with between 6-9 main veins radiating out from the centre where the stem joins. Petioles (stems) are up to 25cm long!

8th July 2009, Ainsdale dunes, Southport, Lancs. Photo: © RWD
Between 6 and 9 veins radiate from the centre, forking when half-way into several fractal branches. The leaves are shallowly crenate (having well rounded 'teeth').

8th July 2009, Ainsdale dunes, Southport, Lancs. Photo: © RWD
Un-like the leaves of Floating Pennywort (which has almost circular leaves with the stalk in the centre but with a deep cut on one side to the supporting stem) the leaves of Marsh Pennywort are orbicular and peltate, with circular leaves, stem attached to the centre and without a deep cleft in the leaf to the stalk - although it does have slight nicks on the periphery). The flowers are hidden under a canopy of leaves. The leaves vary greatly in size from 8mm to 35mm across and are on petioles (stalks) between 1cm and 25cm long!

7th Aug 2009, dunes slacks, Ainsdale, Sefton Coast. Photo: © RWD
The petioles (leaf stems) can be either glabrous (hairless) or hirsute (with long hairs), it is only if the leaves are very hairy (rather than just sparsely hairy, as here) that it will be Hairy Pennywort (Hydrocotyle moschata) but the BSBI maps only show this as occurring in just one or two locations in the UK, now well gone, not seen since 1970 or before. Perhaps the function of the sparse hairs on the underside of the leaves only is to aid the dripping off of condensation and water droplets.

10th Sept 2015, Hilbre Island, West Kirby, Wirral. Photo: © RWD
At first your Author thought he had found the rare flowers of the mostly vegetatively propagating plant, but closer inspection revealed that he was too late for those; these are the minuscule seed pods (fruits), just a little larger than a millimeter across each (there are three here). The flowers are hermaphroditic (bisexual).

26th July 2004, Photo: © Bastiaan Brak
The flowers are in an 'umbel' with 3-6 at the summit, and between 1 and 3 whorls of flowers below. Your Author counts 11 flower in the left-most clump. There are 3 more clumps in the photo; a central one with only un-opened flowers. The flowers (which are hermaphroditic aka bisexual) are white with 5 near-actinomorphic petals with a central pale green stylopodium with 5 white anthers fanning away in a star shape (left-most opened flower). Unopened flowers are like little pink microphones, with 5 sepals wrapped up into a ball atop a tapering stalk. The fruit are green at first, then purplish, wide and flat, wider than they are high and topped off with a pale green stylopodium from which two stubby white styles diverge.

The flowers are 3mm across. The fruit about 2mm wide; wider than long and only maybe 0.5mm thick, almost flat, and covered in brownish resinous dots.

Parts of three of the round but crenately-toothed leaves occupy the periphery of the photo.

10th Sept 2015, Hilbre Island, West Kirby, Wirral. Photo: © RWD
The fruits are so small and narrow as to be almost translucent white with cream or greenish or pinkish hues. Tiny stylopodiums cap styles cap the fruits, each having a pair of short, divergent, remnant styles atop. A ring of a few bracts sit below the fruits. This is similar to an umbellifer, albeit on a miniature scale, but is also dis-similar enough to be assigned a differing Family and Genus.

10th Sept 2015, Hilbre Island, West Kirby, Wirral. Photo: © RWD
These young fruits are flatter on one side (by about 1:2) with two slight elongated dimples on the two larger sides. According to the text books, these fruits are about 1.65mm x 2.05mm (± 10%). It is covered in resinous dots, which according to the books are brownish, so these, being whitish, must not be fully ripe yet.

Some similarities to : Navelwort (the leaves only)

No relation to : Wall Pennywort [a plant with similar name]

Marsh Pennywort does not at first glance look like an umbellifer, but closer inspection of the fruits or of the flowers (of which your Author has not seen yet) reveals the relationship; it was once called an atypical umbellifer but re-evaluation by taxonomists led them to move the Pennyworts out of the Umbellifer family into a new family they called Hydrocotylaceae which contains but one genus, Hydrocotyle to which the Pennyworts have been assigned. Besides Marsh Pennywort there are only four Pennyworts within this Genus:

  • Hairy Pennywort (Hydrocotyle moschata)
  • New-Zealand Pennywort (Hydrocotyle novae-zeelandiae)
  • Floating Pennywort (Hydrocotyle ranunculoides)
  • Marsh Pennywort (Hydrocotyle vulgaris)

The single peltate (drawing-pin shaped) leaves, which are about the diameter of an old penny across, and with rounded (crenate) teeth, belies the fact that under-ground runners sprout many more leaves along their length, of various sizes up to about 4cm across. The runners root at every node where a leaf petioles strike up above the ground. Very few of the plants flower (or in turn yield fruits); most of the plant reproduces vegetatively.

It was once
  Hydrocotyle vulgaris  ⇐ Global Aspect ⇒ Hydrocotylaceae  

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 BSBI maps


Hydrocotyle vulgaris

Pennywort Family [Hydrocotylaceae]  

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