Sagittaria sagittifolia

Sagittaria sagittifolia, also known as arrowhead, is an aquatic perennial plant.  Sagittarias have dephosphating properties used in water treatment. This species offers white flowers with a purple heart in the middle of its lance-shaped leaves during summer. Hardy, it will be highly decorative in ponds or streams, where it prefers to be planted in full sun at a depth of about 30cm (12in). If the conditions suit it, it will slowly spread through stolons.

Arrowhead belongs to the Alismataceae family. It is a tuberous plant originating from horticulture, 60cm (24in) tall, widespread in the water bodies of temperate regions of Europe, Russia, and China. It blooms in July-August. The flowers are arranged along the stem in whorls of three, with male flowers on top and female flowers below. This plant shows a particularity: it has 3 types of leaves, a phenomenon called leaf polymorphism. The submerged leaves form long ribbons of 1.20m (4ft) and can form real aquatic meadows. The floating leaves are rounded and heart-shaped, while the emergent leaves out of the water are arrow-shaped and acute. The underground stem forms numerous shoots that end in tubercles, which serve for propagation.

Arrowheads are used as dephosphating plants on the edges and in stagnant artificial or natural waters, natural streams, shallow waters, and marshy gardens. To prevent them from becoming too invasive, they can be planted in containers submerged in ponds. The Sagittaria sagittifolia can be used decoratively in a water feature or in an aquatic container on the terrace. This plant is considered invasive in the United States.