Broadleaf Arrowhead is an erect native perennial marsh plant with a naked stem growing 6 to 48 inches high.
Leaves are basal on long stalks that on large leaves may be 2 feet long and very stout. Leaves above the water level are arrow-shaped (said to be 'sagittate') with two descending lobes. Leaves may be as much as 10 inches wide and 16 inches long but there is much variability due to water level or soil moisture if surface water is lacking, but in general, the basal lobes will be equal to or a little longer than the length of the remainder of the blade. Leaves have a distinct vein pattern starting from the leaf stalk attachment point and radiating in curves to each lobe tip and to the leaf margins.
Inflorescence: The inflorescence is a naked stem at leaf level or above bearing 3 to 9 whorls of 3 flowers.
Individual flowers are on stalks up to 1 inch long and are usually separated into male and female flowers, sometimes on the same plant and sometimes on separate plants, although perfect flowers do occur. The one inch wide flowers have 3 white petals and 3 green sepals. The sepals are spreading to recurving and do not enclose the fruiting head. On stems with both flowers the male flowers will be above the female flowers on the stem. Male flowers have 7 to 30 stamens with pale yellow filaments and darker yellow anthers. The female flowers have reproductive parts forming a green rounded mass of pistils in the center of the flower. Some species of Sagittaria have up to 1500 pistils. The 3 petals of both sexes are broad with rounded or slightly pointed tips. Beneath each whorl of flowers are 2-3 linear green bracts that are united for 1/4th or more of their total length.
Fruit: Flowers mature to flattened nutlets that are packed into a dense head. Each nutlet is winged on the margins and has a beak extending from and parallel to the widest portion of the seed. Seeds require at least 60 days of cold stratification for germination.
Habitat: Broadleaf Arrowhead is an emergent plant found in the shallow water or saturated soils of marshes, swamps and other wetlands. It grows from a submerged crown of rhizomatous tubers which will form colonies. Consistent cutting or grazing will result in very small plants. Full sun and rich wetland soil is required. Partial sun will diminish flower production.
Names: The genus name Sagittaria is from the Latin 'sagitta' for 'arrow' referring to the shape of the leaf of this genus and the species name latifolia is also from the Latin 'latus' for 'broad' referring to broad leaves. Other Arrowheads have narrower leaves. The alternate common name of Duck Potato is a reference to the tubers being a food of waterfowl. Over time many former separate scientific names have been consolidated into the current name. One such older name from Eloise Butler's day is Sagittaria variabilis. The author name for the plant classification (of 1805) - ‘Willd.’ is for Carl Ludwig Willdenow (1765-1812), German botanist, a founder of the study of the geographic distribution of plants. He was director and curator of the Botanic Garden of Berlin.
Comparison: A similar plant throughout the growing range of Broadleaf Arrowhead in Minnesota is Northern Arrowhead, S. cuneata. Here the bracts are united less than 1/4th of their length, the seed does not have the beak and the leaf lobes are always shorter than the remainder of the blade.
Above: 1st photo - The inflorescence of one plant and the large leaves of two others behind. Drawing courtesy USDA-NRCS PLANTS Database / USDA NRCS. Wetland flora: Field office illustrated guide to plant species.
Below: 1st photo - The Male Flower. 2nd photo - A stem of female flowers.
Below: 1st photo - The center of the female flower is a mass of yellow-green pistils each with a divided style. 2nd photo - This plant's stem rises from a submerged tuber in shallow water. 3rd photo - A flower stem bearing male flowers.
Below: 1st photo - These flower buds clearly show the whorl of 3 that they form and with the small bracts at the base of the whorl still present. 2nd photo - Summer leaves. 3rd photo - Fall color coming.
Below: 1st photo - Leaf vein pattern radiating from the stalk. 2nd photo - Beginning of seed development - the seed pod formed in the green stage.
Below: 1st photo - Seed development - the mature brown stage. 2nd photo - note the individual seeds are small nutlets that are winged on the margins and a beak extending from and parallel to the widest portion of the seed.
Notes: While Broadleaf Arrowhead is considered indigenous to the Garden area, as Eloise Butler noted it in her Garden Log on Sept. 7, 1907, she also brought in plants on July 10th 1910 from nearby Brownie's Pond and in Sept. 1918 from the Pelican Lake region. In her time an alternate scientific name that she sometimes used was Sagittaria variabilis which is now classified as an older synonym for S. latifolia. Broadleaf Arrowhead is found throughout the U.S. except in Nevada and in Canada is found in all the lower provinces except Labrador. In Minnesota it is found in most counties with the scattered exceptions all in western half of the state.
Six species of Sagittaria are recognized as present and native in Minnesota on the DNR list: S. brevirostra, S. calycina var. calycina, S. cristata, S. cuneata, S. latifolia, and S. rigida. Only the last 4 are widespread and only S. cuneata is confusing with our species.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"