Sweet flag provides habitat for waterfowl. Muskrats eat the rhizomes and wood ducks consume the seed. Description: Sweet flag is a perennial, rhizomatous, iris-like herb. The slightly curved spadix is crowded with small yellowish-green to brown flowers that appear from May to July. Sweet flag has thick, creeping rhizomes with brownish exteriors and white, fleshy interiors.
Adaptation and Distribution: Sweet flag is irregularly circumboreal. In North America it is found from Nova Scotia and Quebec to Minnesota, Alberta and Eastern Washington, south to Florida, Texas and Colorado on wet soils and shallow water in ditches, marshes, river edges and ponds. It prefers full sun and a pH range from 5 to 7.
Establishment: Sweet flag can be propagated vegetative by plant or rhizome division, and by seed. Seed should be planted during the fall or winter in a greenhouse. Fill a 2-inch deep tray with an organic soil mix, scatter seed sparsely on the surface and press firmly into the soil. Do not bury further than 1/8 inch deep. Keep soil moist to saturate. Seed does not require stratification and germinates in less than two weeks. When plants reach 3 to 4 inches transplant into individual 4 inch pots. Pots can be placed in shallow water or irrigated frequently to maintain very moist to saturated conditions. Transplant outdoors 1 foot apart in the spring. With adequate moisture seed can also be planted outdoors spring through early summer or in a cold frame late summer through fall.
Management: Keep soil very moist to saturated; sweet flag does not tolerate droughty conditions. It grows well under seasonal, shallow inundation, however, avoids flooding of newly established plants or seeded areas. Starter fertilizers may be used indoors to improve early growth but are unnecessary once transplanted outdoors into a rich soil. The spadix will turn brown as the seed ripens in late summer or early fall. Seed can be planted immediately or stored in low humidity refrigeration.
