Flower:

Flowers are whorled in groups of 3 in a spike-like raceme up to 1 foot long. There are usually both male and female flowers on the same stem, but sometimes a stem has only 1 gender. Both genders are about 1 inch across with 3 broad white petals and 3 small pale green sepals behind the flower. Female flowers have a bulbous green center, covered in tiny pistils.

Male flowers have a group of golden yellow stamens in the center. At the base of the whorl are 2 or 3 papery bracts that are shorter than the flower stalks. One plant has 1 or more spikes, with 3 to 9 whorls of flowers on each. The spike may be taller or shorter than the basal leaves.

Leaves:

A rosette of basal leaves surrounds the flowering stems. Leaves are toothless, hairless and arrowhead shaped with the lower lobes at least half as long as, and usually up to a little longer than, the remainder of the blade. Leaves are up to 16 inches long but are usually about half that. The width is highly variable. In shallow water or drier soil conditions leaves are broad; they are narrow when the plant is submerged in deeper water (see more photos below). The leaf stalk is up to 2 feet long.

Fruit:

Fruit is a head of beaked seeds, that eventually turns dark brown.

Notes:

There is more than one species of arrowhead, with similar flowers, but Broad-leaf Arrowhead is the most common. Ways to distinguish them are the size of the bract at the base of the flower whorls, the size of (or absense of) the lobes at the base of the leaves, and the shape of the fruit.