Flowering rush as a pond plant: position and care

Flowering rush (Butomus umbellatus) is a native marginal plant for the shallow edge of a pond. From a clump of narrow, upright leaves rise bare stems, each topped with an umbel of light pink flowers. The plant grows 30 centimetres to one and a half metres tall. Flowering rush blooms from June to September and needs full sun.

Flowering rush at a glance

Leaf

April to October

Flower

June to September

Fruit

August to September

JanFebMarAprMayJunJulAugSepOctNovDec

How do you recognise flowering rush?

Start with the leaves. All of them grow straight from the ground and stand upright. Each leaf is long and narrow, a little twisted and three-sided at the base.

The flower stems are round, sturdy and bare, often tinged red. At the top sits a loose umbel, spread like the ribs of an umbrella. Each flower has its own stalk from the tip of the stem. The flowers are light pink with dark veins and 1.6 to 2.6 centimetres across. In the centre are nine red stamens. Up close, the flowers smell of bitter almond. After flowering, small reddish-purple fruits form in groups of six.

Without flowers, flowering rush looks like a bulrush or a true rush. In that case, look at the base of the leaf: it is three-sided. Cultivars exist too. 'Rosenrot' flowers mid to deep pink, 'Schneeweisschen' white.

Where does flowering rush grow best?

Choose a sunny pond edge, a spot that gets more than six hours of direct sunlight around midsummer. The base of the plant does best in still water.

Two places in a garden do not suit flowering rush:

• A dry border. Flowering rush is a marsh plant and needs wet soil or shallow water.
• A pond without a shallow edge. Flowering rush does not belong in the deep zone of a pond.

In autumn the leaves die back. Until spring, a clump of straw-brown leaves remains, partly bent over onto the water.

JulyJanuaryOne pond edge with flowering rush, in July and in January. This is a generated image, not a photograph.

In the app you can first try out where those narrow clumps go in your own garden. The app draws the plant at a grown plant's width, not at pot size.

Planting and caring for flowering rush

Plant flowering rush in spring, when new growth comes up again from the roots. Nurseries sell it in a small pot or in a pond basket. Set the plant so that there is usually 10 to 30 centimetres of water above its base.

One nursery gives a planting density of 12 plants per square metre. On planting day that looks like a bare edge with a few green blades. Watering is not needed as long as the base stays under water.

Many bird species breed from March through July. Before you remove stems in those months, check whether there is a nest in the clump.

If a piece is left over after dividing, never put it out in a ditch, a lake or any other natural water.

What goes wrong with flowering rush?

No flowers appear. Check the water depth. In deep water flowering rush does not come up above the surface, and the plant does not flower. Move the plant to shallower water.

Small reddish-brown or dull green aphids sit on the leaves and buds. That is probably the water lily aphid. Damage usually only happens in summer, when a dense colony forms. Wipe the aphids off the leaves and buds.

The leaves turn yellow and brown. In autumn that is normal, because the plant loses its leaves every year.

Which insects and birds use flowering rush?

The flowers give nectar and pollen. Many hoverflies visit them, and hoverflies in turn are food for dragonflies. That makes flowering rush a good fit for a pond meant for dragonflies.

A dense edge of flowering rush, yellow iris or water mint also helps against the grey heron. Such an edge makes it harder for the heron to reach the fish in your pond.

Is flowering rush poisonous or edible?

No hazards are known for flowering rush. That tells you nothing about eating it, though. The rhizome is eaten, but only cooked, peeled and with the rootlets removed. More than half of that rhizome is starch.