Plant of the Week
Giant Arrowhead (Sagittaria montevidensis)
By Robinson Sudan
An aquatic plant, Sagittaria montevidensis is stemless and rhizomatous with its young leaves growing submerged. As the leaves mature, they become arrowhead shaped up to 28 centimeters long and 23 centimeters wide. Its petioles can be three-quarters of a meter long and over 7 centimeters thick. Shorter than the leaves, the inflorescences have 2 to 3 centimeter flowers arranged in whorls. The thick pedicels end in 3 green sepals and an equal number of cream to white colored petals with most subspecies having burgundy colored spots at their bases. These attractive flowers can be found from June to September. Giant Arrowhead is insect pollinated.
Though aquatic, Sagittaria montevidensis is often found at pond edges in shallow, ephemeral water, sometimes occurring in tidal mud flats. This species has a broad distribution at the continental scale, occurring across much of North and South America. However, the distribution across the United States is somewhat disjoint, known to occur in some New England and Middle Atlantic States, across the southeastern states, Michigan, and in California.
Because of the disjoint distributions, Sagittaria montevidensis is considered vulnerable in Michigan.