Arrowheads & Water-plantains

Common Arrowhead Narrow-leaved Water-plantain Common Water-plantain Common Arrowhead

What are they?

Arrowheads and Water-plantains form the family Alismataceae, a group of plants with flowers bearing three sepals and three petals and sometimes with male and female flowers carried separately on the flower spike. Also included here is Flowering-rush, which is closely related but in its own family, the Butomaceae. These plants grow as submerged aquatics or as plants of wet mud. When growing in water, the submerged leaves are often narrower and quite different to the aerial leaves.

Where are they found?

As aquatic plants, these species grow as emergents along still or slow-moving water in ditches, dykes and along main waterways. Some species may also occasionally be found in seasonally flooded land where bare mud is available.

Identification

Flowering-rush is unmistakable when in flower, while Common Arrowhead can readily be told by its leaves, which are shaped like arrow heads. The water-plantains can be tricky and identification relies on careful study of aerial leaf shape, petal shape and precise detail of the style placement.



Common Arrowhead      Sagittaria sagittifolia

Native. Scattered around the region and growing as an emergent plant of slow-moving rivers, usually in the mid section of the larger rivers. Flowers July to August. In our region, the arrow-shaped leaves emerging from water are diagnostic.

Common Arrowhead Common Arrowhead Common Arrowhead Common Arrowhead
Flower spike
Flower
Leaves
Seed capsules


Common Water-plantain      Alisma plantago-aquatica

Native. Widespread in wet places, growing both as an emergent from standing water and on wet mud. Flowers June to August. Small, three-petalled flowers carried in a large, much-branched head. Petals slightly pointed at the tip; leaves rounded to more or less cordate at the base. Under a hand lens, the style can be seen to be about half way up the side of the fruit.

Common Water-plantain Common Water-plantain Common Water-plantain Common Water-plantain
Flower spike
Flower
Leaf
Position of style
shown by red line


Narrow-leaved Water-plantain      Alisma lanceolatum

Native. A rare plant found as small, isolated populations in good-quality wetland sites. Flowers June to August. Small, three-petalled flowers carried in a large, much-branched head. Petals not pointed at the tip; leaves spear-shaped, cuneate at the base. Under a hand lens, the style can be seen to be more than half way up the side of the fruit.

Narrow-leaved Water-plantain Narrow-leaved Water-plantain Narrow-leaved Water-plantain Narrow-leaved Water-plantain
Flower spike
Flower
Leaf
Position of style
shown by red line


Flowering-rush      Butomus umbellatus

Native. Grows as an emergent aquatic plant along the main river systems. Generally rather local, but common along some stretches of the Wensum in Norfolk. Flowers July to September. Petals and sepals somewhat similar, giving the appearance of a six-petalled flower. Easily overlooked hen not in flower, but the leaves often have a fairly distinctive spiralled look.

Flowering-rush Flowering-rush Flowering-rush Flowering-rush
Habit
Flowers
Flower
Leaves