Sagittaria latifolia is a native aquatic species found in Wisconsin, and in fact, throughout the United States except for Nevada and Alaska. Throughout its range, it is called by many names including the following: Arrowleaf, Broadleaf Arrowhead, Duck Potato, Indian Potato, Katniss, Swan Potato, Swamp Potato, Tule-Potato, Wapato, Wapatoo, Wappato and Wapati. I will refer to it here as duck potato, since that is our local norm.
Duck potato grows in sunny spots in shallow standing water of marshes, ditches, lakes, sloughs, ponds, bogs, rivers and streams. There is conflicting research as to what it prefers for water level. One source states that duck potato does especially well in areas where water levels fluctuate throughout the year, while another source insists that water levels should remain constant. Perhaps it does equally well no matter whether water levels change or not. In perfect conditions, huge colonies can form, making a ribbon-like band following the banks of a stream, river or lake. It is an emergent plant, meaning that it is rooted in the lake, river or pond bottom but its stems and leaves extend above water.
Leaves are large and unmistakably arrow-shaped. Sagittaria means “arrow.” Latifolia is derived from two Latin words, latus, meaning “broad” or “wide” and folius, meaning “leaved.”
Duck potato stands from 1 to 5 feet tall. Leaves vary in size from 4 to 12 inches long and 2 to 6 inches wide. The sturdy flower stalk is separate from the leaves, but just as tall. Each stalk produces 2 to 15 whorls of pretty white, 3-petaled flowers about an inch across. Flower centers are green or yellow. Sepals are ovate, and bend backward by fruiting time. In late summer, the flowers develop into round clusters of seeds – up to 20,000 viable seeds per plant! Seeds are winged achenes 2 to 4 mm long, with a beak projecting an additional 1 to 2 mm. Near the end of summer, the leaves and flower stalk begin to die back and all the nutrition they’ve stored goes down into the rhizomes and the tubers that grow at the ends of them.
Tubers grow like numbers on a clock around the main stem of the plant. The tubers are found at the end of rhizomes up to three feet away from the plant and from 6 to 16 inches deep in the muck. Tubers range from acorn-sized to golf-ball sized. Colors are white, pink or purplish, once the muck is washed off.
Strangely, given that one of the names for S. latifolia is “duck potato,” it is very difficult for ducks to actually eat the tubers. They are simply buried too deeply in the muck for ducks to reach. Canada geese, being larger, are able to dig in the muck to unearth the tubers and actually swallow them whole. Though mallards and other shallow water ducks are unable to access the tubers, they do eat the emergent shoots in spring and the seeds in fall. Seeds are also eaten by other waterfowl, songbirds and wading birds. The foliage provides cover for fish and aquatic insects. In the animal kingdom, beavers, porcupines and muskrats eat the entire duck potato plant.
Along with the wildlife benefit, duck potato improves water quality by removing excess nitrogen and phosphorus. It is also able to tolerate and assimilate heavy metals.
Duck potato can be propagated in several ways. Tubers are planted in spring by pushing them into the muck about 2 to 3 inches in areas where water is from 6 to 12 inches deep. They are buoyant, so be sure they are secure or they will float to the surface. Here is what the USDA recommends for spacing: “Site quality will dictate plant spacing. Under ideal site conditions plants can be spread up to 6 feet apart and still attain stand closure within one growing season. On degraded or critical sites it is advisable to reduce plant spacing to 1 to 2 feet.”
It can also be propagated by seed. Again from the USDA: “The achenes are easily harvested, cleaned, and broadcast sown. Prior to spring sowing, the seeds need a three month moist stratification treatment. Sow on to well worked, saturated soils. Germination occurs under direct sunlight with temperatures ranging from 80° to 90°.”
You may also find duck potato available bare root or potted. When planting either of those, ensure that the leaves are not submerged at planting time.
No fertilizer or added nutrition is necessary for duck potato to thrive. The only requirement is a saturated soil.
There are six species of Sagittaria found around the Great Lakes and Upper Midwest:
- brevirostra (Midwestern arrowhead)
- calycina (Mississippi or Long-lobed arrowhead)
- cuneata (Northern arrowhead or Arum-leaved arrowhead)
- graminea (Grass-leaved arrowhead)
- latifolia (Common arrowhead)
- rigida (Sessile-fruited arrowhead)