Richard John Torrens
Freshwater habitats

Aquatic life

Frog Bit and Fringed Water-lily

It may seem odd to include Hydrocharis morsus-ranae - Frog Bit and Nymphoides peltata Fringed Water-lily together. Botanically they are not closely related. However to an amateur naturalist, they appear at first sight to be very similar indeed and, growing together in a pond, close inspection is required to determine which is which! Look at the pictures below.

Click on a picture for the full sized version

Nymphoides peltata Nymphoides peltata Hydrocharis morsus-ranae

Moat at Oxborough Hall Moat at Oxborough Hall Royal Military Canal

2004 Aug 27 2004 Aug 27 2004 Aug 21

Pictures 1 and 2 show the moat at Oxborough Hall in Norfolk almost completely covered by Nymphoides peltata - Fringed Water-lily. Picture 2 is a close-up showing the leaves several layers thick and the flowers.

Picture 3 is on the Royal Military Canal near Appledore, in Kent. (Royal Military Canal www site) On first look, you can see the yellow flowers of Nymphoides peltata - Fringed Water-lily but look more carefully and a few white flowers can also be made out: these are Hydrocharis morsus-ranae - Frog Bit and this patch actually contains rather more frog-bit that fringed lily! Both species do so well in the canal that in certain places there are piles of them, mixed with fringed lily and other water plants, where the canal has been cleared.

Nymphoides peltata Fringed Water-lily

Normally this grows in the bottom mud, in water up to a metre or so deep (ideal depth is probably around 30-50cm) and sends up leaves on long stalks. The plant does not have a thick rhizome quite the same as other water lilies but instead the rhizome is more like a stolon and creeps in the mud, forming a leaf node every 30cm or so. Sometimes these creeping rhizomes leave the bottom and grow in the water, just below the surface, suspended by the leaves. In this state, the plant is very similar to frog-bit! It is however a close relative of the true water-lilies.

Nymphoides peltata is a British native and grown in ponds and slow rivers in east and central England, from Sussex and Kent, through Berkshire, E. Gloucester, Shropshire, S York and the Cambridge fens (I quote from Clapham, Tutin and Warburg). It is an excellent pond plant and is suitable for small ponds as it has leaves smaller than any true water-lily. It is also very suitable for (cold water) aquaria, but (like most cold-water plants) needs quite a strong light for good growth.

Hydrocharis morsus-ranae - Frog Bit

This is a member of the hydrocharidae, so is closly related to Water Soldier stratiotes aloides. Like the Water Soldier, it grows free-floating in the water, suspended by its floating leaves. It sends out stolons (runners) which form new plantlets so resembles the floating form of fringed lily.

Hydrocharis morsus-ranae is a British native and grown in ponds and ditches, usually in hard water. It's scattered throughout England from Devon and Kent to S. Lancashire and Durham, parts of Wales Generally local and probably diminishing (say Clapham, Tutin and Warburg in 1952). It is now on the red-list of nationally endangered plants, so should be encouraged in garden ponds.

So it is not a common plant. It is said to be a plant of the Norfolk Broads: indeed in April 2006 I did see one newly risen plans in Cockshoot Dyke - which feeds Cockshoot broad, one of the Broads which is now restricted to boats and which is being cleaned up as a wildlife habit.

Frog Bit over-winters by means of turions, or winter buds, which fall to the bottom to over-winter. The plant starts producing these in late August or early September. When water temperatures start to rise in late April or early May, light penetrating to the bottom starts growth and the young plant rises to the surface. It follows from this that the plant needs clean water) or not enough light will penetrate to start re-growth) and also that it does best in relatively shallow water: the earliest spring plants to appear to be those that are in the shallowest water! The plant is. it seems. only on the surface for 4 to 5 months of the year!

Frog-Bit or Fringed Water-lily?

A couple of photos should show how similar these two plants can look. Both were taken 5th May 2006.

The two leaves at the top belong to the fringed water lily: you can see its runner floating below the water surface. Below that are leaves of three frog-bits. The frog-bit leaves are a little rounder, especially at the tip.

You can also see a tadpole or two, and (top left) some ivy-leaf duckweed. At bottom is a frond of spiked water-milfoil.

A different part of the pond. Frog-bit (Centre, left), fringed water lily (Centre) and broad-leafed pondweed (Bottom, centre) can be seen, as well as a leaf of great spearwort (bottom, right). Notice the way the early leave of many (most?) water plants have a distinct reddish tinge. Picture on right shows the turions of the frog-bit, with two water-soldier turions.

Top of page

Page Information

Document URI: nathist.torrens.org /Aqua/Plants/FrogFringe.html
Last modified: Mon, 08 Jul 2024 09:18:17 BST
Page first published 14th November 2002
Page written and © by Richard John Torrens


Nymphoides peltata	Nymphoides peltata	Hydrocharis morsus-ranae
Moat at Oxborough Hall	Moat at Oxborough Hall	Royal Military Canal
2004 Aug 27	2004 Aug 27	2004 Aug 21