Arrow-head - Sagittaria sagittifolia
The name underlines the characteristic that makes this plant unmistakable: its arrow-shaped stalk and leaves.
Actually this species, like many other plants that live in semi-submerged conditions, is heterophyllous (i.e. it has differently shaped leaves).
The first leaves growing like a fan from the underground tuberiform stem are slender and elongated (ribbon shaped): these are the spring leaves adapted to a submerged and floating life and can be confused with those of the more common Lesser Water-plantain; the typically arrow shaped leaves only grow later, adapted to carry out their function in an aerial habitat.
The flowers, seen in full summer, have three characteristic round, white petals, pinkish-purple in the centre. The unisexual flowers are arranged in whorls of three around a flowering stem which grows above the leaves.
As normally happens, the male flowers are in a higher position on the inflorescence and the females flowers lower down.
The perennial part of the plant consists of underground bluish coloured tuber, serving for the conservation and over-wintering of the plants, storage of nutrients (starch) and vegetative reproduction.
The Arrow-head grows in eutrophic habitats, but it does not tolerate other kinds of pollution very well. In Italy it is considered a rare plant; in the wetlands of the lower Arno Basin (Fucecchio, Sibolla, Bientina) it is drastically falling in numbers.
