Flower:

Flowers are whorled in groups of 3 in a spike-like raceme at the top of a naked stem. There are usually both male and female flowers on the same stem, but sometimes a stem is all female. Both genders are about 1 inch across with 3 broad white petals and 3 small pale green sepals behind the flower. Female flowers are stalkless or nearly so, and have a bulbous green center, covered in tiny carpels.

Male flowers are on long, slender stalks and have a group of yellow stamens in the center. The stamen stalk (filament) is stout and covered in short yellow hairs.

Behind the flower are 3 small pale green to brownish sepals. At the base of the whorl are 3 broadly triangular to egg-shaped bracts, less than ¼ inch long. The bracts shrivel up quickly, the brown, papery remains persisting through fruiting. A plant has 1 or more flowering stems, each with 2 to 8 whorls of flowers.

Leaves and stems:

A rosette of toothless, hairless basal leaves surrounds the flowering stems. Emersed leaves are typically narrowly lance-elliptic, the blade up to 6 inches long, on 3-sided stalks up to 20 inches long.

Leaves may be up to 4 inches wide in shallow water or drier conditions, and rarely blades may have narrow lobes at the base.

Submersed leaves are more grass-like, lance-linear, tapering to a sharp point at the tip. Flowering stems are weak and often bent near the lowest whorl of flowers. This species has stolons (horizontal stems) but not rhizomes.

Fruit:

Fruit is a globular head of beaked seeds up to ¾ inch in diameter and turns a deep reddish color as seeds ripen. The seed's beak projects at an upward angle with a slight hook at the tip.

Notes:

Of the 6 Sagittaria species in Minnesota, Sessile-fruited Arrowhead is most easily distinguished by (you guessed it) its stalkless female flowers and fruits. The leaves are similar to Crested Arrowhead (Sagittaria cristata) and Grass-leaved Arrowhead (S. graminea), both of which have long, slender stalks on all its flowers and fruits. The broader leaves of Sessile-fruited Arrowhead may resemble those of a Water Plantain (Alisma species) but their flowers are in branching clusters and are only about ¼ inch across.