Helenium autumnale aka Sneezeweed

Helenium autumnale, or autumn sneezeweed, belongs to the aster family. This perennial grows across much of North America. Its native range reaches from subarctic America into the United States. It grows in damp meadows, marshes, thickets, and along shores. In gardens, it forms upright clumps with branching stems. Plants reach about 3–5 feet [0.9–1.5 metres] tall, sometimes more. Spread estimates differ between sources. RHS gives up to 1.6 feet [0.5 metres]. NC State gives 2–3 feet [0.6–0.9 metres].

The green stems have ridges or narrow wings. Dark green leaves grow in an alternate pattern along them. Each simple leaf lacks a stalk and usually has toothed edges. Leaves range from oval to narrow and lance-shaped. They reach about 0.25–0.5 feet [0.08–0.15 metres] long. The foliage dies back for winter. Yellow flower heads form clusters above the leaves. Their raised centres range from yellow to brown. Each drooping ray has three lobes at its tip. Flowers appear from late summer into autumn, often August through October. Fruit follows in October and November.

Give this plant full sun and soil that holds moisture. It also tolerates some shade, according to NC State. Rich soil with plenty of organic matter suits it. Sources list clay, loam, sand, and chalk as suitable soils. It accepts acid, neutral, and alkaline conditions. Keep the ground moist; the plant also tolerates wet soil. Its hardiness range is USDA zones 3–8 and RHS H7. Tall stems may need stakes or other support. Divide clumps every two or three years to sustain growth. Removing spent flowers can extend the bloom season.

Use sneezeweed toward the back of borders or beside ponds. It also suits meadow, prairie, cottage, and rain gardens. The flowers work as cut flowers. Bees gather pollen and nectar, and butterflies visit the blooms. Deer and rabbits tend to leave the plant alone. Most plants have few serious pest or disease problems. Watch for leaf spot, rust, and powdery mildew. The species can be weedy in some settings.

No edible uses are known. Eating large amounts can cause vomiting, breathing trouble, and convulsions. The plant also poisons ruminants. Contact may irritate the skin of sensitive people. Past uses included powdered leaves and flower heads to trigger sneezing. People used leaf infusions as laxatives. These historical uses do not establish safe home treatments.