Aquatic Plants of Pennsylvania. Timothy A. Block
also an important source of food for wildlife. The achenes are eaten by ducks.
Submersed plants with ribbon-like leaves can be confused with water-celery (Vallisneria americana) or some of the bur-reeds (Sparganium spp.), but the venation is different and the leaves are not as strictly parallel-sided. See additional discussion under water-celery.
Sagittaria cuneata—achene ×5
Sagittaria cuneata ×1/4
| Grass-leaved arrowhead | Sagittaria graminea Michx. |
Native
Rooted, emergent or submergent perennial
Grass-leaved arrowhead is a rhizomatous perennial; it grows as an emergent or completely submersed where it sometimes forms a coarse turf. Underwater, the leaves are stiff, linear, and tapered to an acute tip; length and width can be highly variable. Emergent leaves typically develop an elliptical blade; lobed leaves are rare. The flowering stem contains 2–12 whorls of flowers; both male and female flowers are borne on individual pedicels. Flowering occurs from June to early August.
Grass-leaved arrowhead has a range covering the eastern half of the United States and adjacent areas of southern Canada. In Pennsylvania it occurs in the eastern half of the state in shallow water of lakes, ponds, and streams and on tidal mudflats.
Stalked female flowers distinguish this species from sessile-fruited arrowhead. In the absence of an inflorescence it is impossible to differentiate grass-leaved arrowhead from the sterile rosettes of other species based on appearance alone.
Sagittaria graminea ×1/2
Sagittaria graminea—juvenile rosette ×1/2
Sagittaria graminea
| Duck-potato, wapato | Sagittaria latifolia Willd. |
Native
Rooted, emergent perennial
Duck-potato is one of the most common emergent plants of lake and pond margins, swamps, marshes, and stream edges throughout Pennsylvania. The leaves are arrow-shaped with 2 backward-pointing basal lobes; the width of the main part of the blade and the lobes varies from plant to plant, ranging from very narrow to broad. Both leaves and flowering stems of this native perennial, which are up to 0.6 m tall, arise directly from a large, starchy, edible corm; stolons may also be present.
The flowering stalks bear 2–15 whorls of 3 flowers each; the lower whorls contain female flowers; male flowers are borne above. The flowers are white and 0.5–2 cm across; flowering occurs from July to early September. Fruiting heads are round and globe-like to somewhat flattened, up to 2.5 cm across, and the tiny, 6 mm-long achenes have a beak extending at a 90-degree angle to the body of the fruit.
The total range of arrowhead extends from Newfoundland and New Brunswick west to British Columbia, and south to northern Florida, Alabama, Louisiana, Texas, California, and Mexico.
The starchy corms of arrowhead were an important food for many Native American tribes. Known as “wappatoo” or “katniss,” the corms were prepared by baking, roasting, or boiling; they were also stored for winter use. Ducks, geese, and muskrats also eat the corms and seeds of this plant.
Sagittaria latifolia—inflorescence ×1/2
Sagittaria latifolia—leaf variation ×1/2
Sagittaria latifolia
Sagittaria latifolia
Sagittaria latifolia—achene ×5
| Sessile-fruited arrowhead | Sagittaria rigida Pursh |
Native
Rooted, emergent or submergent perennial
Sessile-fruited arrowhead is a stoloniferous perennial with emergent or submergent leaves; corms also are produced. Underwater leaves are stiff, flattened, about 1 cm wide, and narrowed to an acute tip. Emergent leaves are typically elliptical or sometimes even develop a sagittate blade. Flowering can occur on emergent plants or those that are submersed in water 1–2 m deep. The inflorescence is characterized by female flowers that are attached directly to the main axis (sessile). In addition, the flowering stems are typically bent at the lowermost whorl of flowers.
Sessile-fruited arrowhead grows from Prince Edward Island to Wisconsin and south to Virginia and Missouri. Disjunct populations are known in Washington and California. In Pennsylvania, it is a plant of lake and pond margins, mudflats, and stream edges at scattered locations throughout. Flowering occurs from late July to late August.
If inflorescences are present, sessile-fruited arrowhead can be distinguished from the very similar grass-leaved arrowhead by the sessile female flowers. The two species are almost impossible to differentiate based on sterile rosettes alone.
Sagittaria rigida—inflorescence ×1/2
Sagittaria rigida—leaf variation ×1/5
Sagittaria rigida ×1/4
Sagittaria rigida
| Subulate arrowhead | Sagittaria subulata (L.) L. Buch |
PNHP
Native
Rooted, emergent or submergent perennial
This perennial species spreads by stolons to form a turf in the freshwater intertidal zone along the Delaware River and some of its tributaries. The plants are completely exposed at low tide and inundated at high tide. The 2.5–5 cm-long leaves are linear, sometimes with just a suggestion of an expanded blade at the tip. Flowering stems are slightly taller than the leaves and bear 2–3 whorls of flowers. Sepals