Arrowhead (Sagittaria sagittifolia): planting and care

Arrowhead (Sagittaria sagittifolia) is a native marginal plant for shallow fresh water. Leaves shaped like the point of an arrow stand above the water. From June to September the plant flowers white, with purple at the base. Arrowhead grows 30 to 90 centimetres tall and wants a sunny spot.

Arrowhead at a glance

Leaf

May to October

Flower

June to September

Fruit

August to October

JanFebMarAprMayJunJulAugSepOctNovDec

How do I recognise arrowhead?

Start with the leaves above the water. Each one is deeply arrow-shaped, with two pointed lobes reaching backwards, on a long stalk. Earlier in the year the plant makes other leaves. First, long ribbon-like leaves grow under water. Floating leaves follow, oval to oblong. The stems and leaf stalks are three-sided.

The flowers sit in whorls, usually of three, on a long stem above the water. Each flower measures 2 to 2.6 centimetres and has three white petals, purple at the base. The male flowers grow at the top of the stem, with many dark purple stamens. The female flowers are a little smaller. Each one grows into a ball of flat fruitlets, half a centimetre in size.

Do not mix arrowhead up with broadleaf arrowhead (Sagittaria latifolia). That species comes from North America and grows wild here in a few places. Its leaves are much broader and its petals are pure white. Nurseries also sell 'Flore Pleno', a cultivar with double flowers.

Where does arrowhead grow best?

Arrowhead belongs in full sun: more than six hours of direct sun a day around midsummer. The plant grows with its base in shallow water, on a bottom of clay, loam or sand. Still or slow-flowing fresh water suits arrowhead best.

Not every wet corner of a garden will do:

• A border or lawn with no water. Arrowhead is a marsh plant, and its base belongs under water.
• A small pond that must stay open. Runners as much as a metre long grow from the rootstock, each with a tuber at the end. That way the plant keeps moving further into the water.

In autumn the leaves die back. The tubers on the runners stay in the pond bottom. In January all that is left at that spot is a few broken brown stalks lying on the water.

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

On a plan of your own plot, to scale and with the buildings around it, you can see where a pond edge like this could go in your garden.

Planting and caring for arrowhead

Nurseries sell arrowhead in a small pot. Until mid-April, some also deliver loose tubers. Place the plant so that there are 10 to 40 centimetres of water above its base.

If you plant more than one, keep about 50 centimetres between plants. That is the smallest spread in the table. On planting day this looks like a lot of open water. The runners fill that space later without any help.

Watering is not needed, as long as the base stays under water. Pruning is not needed either. Only pull out the runners that reach further than you want.

Arrowhead problems and what to do

Only long, narrow leaves appear, and no flowers. In spring that is normal: the first leaves are ribbon-like and stay under water. If nothing changes, look at the water. In fast-flowing water arrowhead makes only ribbon leaves and does not flower. A spot with still water helps.

The leaves turn yellow and flop over. In autumn that is to be expected. Above the water the plant dies back.

Young plants pop up all over the pond. Those are the runners, each with a tuber at the end. Pull them out, tuber and all.

Pests and diseases are rare on arrowhead.

Which birds and insects use arrowhead?

Insects pollinate the flowers. Which insects and birds use arrowhead has hardly been described for this species.

Is arrowhead poisonous or edible?

Arrowhead is not known to be poisonous. That does not mean you can eat the plant. In East Asia people do eat the tubers, after cooking. Raw tubers are not fit to eat.