Frogbit (Hydrocharis morsus-ranae): pond care and price

Frogbit (Hydrocharis morsus-ranae) is a native floating plant for a pond or ditch. Its round leaves lie loose on the water, and the roots hang free beneath them. From June to August, white flowers with three petals rise above the water. Give frogbit still water in full sun.

Frogbit at a glance

Leaf

April to October

Flower

June to August

Fruit

no noticeable fruit

JanFebMarAprMayJunJulAugSepOctNovDec

How do I recognise frogbit?

Start with the leaf. Each one is almost round and about 3 cm across, with a deep, heart-shaped notch at the base. The leaf feels fleshy and has a smooth edge, without teeth. On the water the leaves sit together in small rosettes.

Long white roots hang in the water under each rosette. Most of the time they do not reach the bottom. A long stem, called a runner, grows from a leaf axil, and a new plant forms on it.

The flower is 2 to 3 cm across and sits on a stalk above the water. Its three white petals are yellow at the base.

Fringed water-lily (Nymphoides peltata) has leaves that are nearly as round. The flower tells the two apart: fringed water-lily flowers yellow, with fringed petals. White water-lily also flowers white, but its flowers are much larger: 6 to 20 cm, with 15 to 25 petals.

Where does frogbit grow best?

Frogbit needs full sun. Around midsummer, that means more than six hours a day of sunlight falling straight on the water. The plant grows in shallow, still, sheltered water that is rich in nutrients. In the wild, frogbit turns up in ditches, ponds and sheltered corners of lakes.

Frogbit fails in two places:

• A pond with a pump or a fountain. Frogbit belongs in still water. A current keeps pushing the loose plants away.
• A shallow container that freezes to the bottom. The winter buds rest on the bottom through the cold months, so the water must be deep enough to protect them.

In autumn the leaves and stems die back. Small winter buds of about a centimetre then sink to the bottom. By January nothing lies on the water. In April the buds rise again and start to grow.

JulyJanuaryThe same pond in July and in January. This is a generated image, not a photograph.

In the app your own plot appears to scale, with the neighbours' houses around it. On that plan you can measure for yourself how much room there is for a pond.

Planting and caring for frogbit

Frogbit does not go into soil. Lay the plants loose on the water in spring or summer, while they are in leaf. Out of season, nurseries sometimes sell winter buds instead of plants. Those also go loose into the pond.

There is no fixed planting distance, because the plants drift wherever the wind takes them. Each plant makes new rosettes on its runners. A group spreads that way to between half a metre and a whole metre across. On planting day, a handful of plants therefore looks like very little on a pond.

The plant lives in water, so watering is never needed, and neither is pruning. To keep some open water, scoop a few plants off with a pond net in summer.

Frogbit problems and what to do

The leaves have little tunnels or folded edges, and they rot away. That may be the caterpillars of the brown china-mark moth, a small brown moth with white spots. These caterpillars feed on many kinds of water plant. In most cases, leave them be.

There are snails on the leaves. Frogbit can be troubled by water snails. Most pond snails feed mainly on dead plant material and algae, and they usually leave healthy plants alone.

You see hardly any flowers. Each flower is open for one day only. On a male flower stalk, usually just one flower opens at a time. Check the pond on a few days in a row in July.

Everything has gone in autumn. That is normal. The plant spends the winter as a bud on the bottom and comes back in April.

Which insects and birds use frogbit?

Frogbit is on the list of plants for a dragonfly pond, among the water plants with floating leaves. Dragonflies and damselflies need water, and plants in and around that water as well.

At the base of each petal, the flower has a nectar scale: a tiny scale that holds nectar. Records of which insect and bird species use frogbit are scarce.

Is frogbit poisonous or edible?

Frogbit is not known to be poisonous. That only means no risk is known in a garden or pond. It does not mean you can eat the plant.