Helenium amarum aka American Sneezeweed

Helenium amarum is an annual in the daisy family, Asteraceae. Its common names include bitterweed and sneezeweed. Its native range spans the central and southern United States. It also reaches northeastern Mexico and the Caribbean. It grows on open ground, roadsides, fields, and pastures. Other sites include open woods and land disturbed by people.

This bushy, upright plant has a scent and branched stems. It often stands about 1 foot [0.30 m] tall. Less often, it reaches 2 feet [0.61 m]. Its spread reaches about 1.25 feet [0.38 m]. The stems have lengthwise grooves and branch toward the top. Narrow, threadlike leaves grow in an alternate pattern. They spread outward or point up along the stems. Leaves reach 0.25 feet [0.076 m] long and bear resin glands.

The yellow flower heads have the form of daisies. Each can reach 0.25 feet [0.076 m] across. Five to ten golden rays ring each flower head. Each ray has three lobes at its tip. The rays droop as part of the flower's form. Bloom runs from August through October. Flowering may start sooner where winters stay warm. The showy heads draw butterflies to the garden.

Grow bitterweed in full sun for the best results. It also accepts some shade during the day. It grows well in sandy or gravelly soil with good drainage. Dry to moderately moist soil suits it. It tolerates drought and dry ground, and needs little care. Removing old flower heads helps it make more blooms. It also sets seed freely in garden beds. Missouri Botanical Garden lists it for USDA zones 3–10. Garden uses include borders, rock gardens, and cottage gardens. It also suits meadows, prairies, and less formal wild gardens. Large groups give a stronger show of yellow flowers.

Serious pest and disease trouble is not usual. Still, powdery mildew, leaf spot, and rust can affect leaves. Its free seeding can make it a weed. Plants For A Future lists no known edible uses. All parts contain gudaldin, which can poison grazing animals. Even small amounts in a cow's diet can taint milk. Honey from its flowers is also reported to taste bitter. The same source records use to clear nasal mucus. It also records sweat-bath use for swelling and dropsy. These are reported uses, not proof of safe treatment.