floating marsh pennywort

Water pennywort has stems that spread horizontally and can float on water. Leaves grow on petioles up to 35 cm long, and are round to kidney-shaped, with 3–7 lobes and crenate to entire margins. Flowers are small, pale greenish white to pale yellow, and come in umbels of 5–13. Fruits are small achenes that can float, helping the seeds to disperse. The South American weevil Listronotus elongatus lays eggs on and eats the floating pennywort, and larvae also eat into the stems, reducing the pennywort's ability to grow. The weevil has been introduced for biocontrol of the floating pennywort into waterways in Britain, following extensive research to establish that the weevil is not a threat in itself.

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