Helenium puberulum aka Sneezewort

Helenium puberulum goes by the name rosilla. It belongs to the daisy family, Asteraceae. Its native range runs from California into northern Baja California, Mexico. It grows in damp meadows, marshes, and on slough banks. In California, these sites lie below 1,970 feet [600 metres]. This plant forms clumps and lives for more than two years. It has soft, not woody, growth and sheds its leaves each year. Gardeners grow it in beds, borders, and gardens for wildlife.

The RHS says plants reach about 5.2 feet [1.6 metres]. Its size table gives 4.9–8.2 feet [1.5–2.5 metres], a wider range. The listed spread reaches 1.6 feet [0.5 metres]. Plants reach full size in two to five years. Thin flaps of tissue run down the stems like wings. Most dark green leaves grow near the base. The round flower heads are yellow-brown. Most lack clear petals, though a few may ring the base. Plants bloom from summer into autumn.

Give rosilla full sun and rich soil with plenty of humus. Keep soil moist, but let excess water drain away. It accepts chalk, clay, loam, and sand. Soil may be acid, neutral, or alkaline. Water well in dry summer spells. Sites may be open or sheltered. The RHS gives it a hardiness rating of H7. This covers cold below −4°F [−20°C]. Plants For A Future lists USDA zones 7–10. These two scales differ; read each on its own.

Rosilla suits sites near the coast and cottage gardens. It also suits informal borders and provides heads for cut flowers. Plants For A Future says it draws wildlife. Cut off spent heads to help it bloom for longer. Divide clumps every two or three years to keep growth strong. Do this in spring or late autumn. In spring, you can also grow new plants from basal softwood cuttings. These are soft young shoots cut from the base. Slugs, snails, and tortrix moth may attack it. Stem and bulb eelworm may attack it too. Diseases may include powdery mildew and leaf spot. Verticillium wilt and viruses may also occur.

Plants For A Future lists raw leaves and flower heads as edible. It gives food use a low rating. It reports no known hazards; this does not prove safety. It lists past uses as wound powders and snuff. Other records note use for colds, scurvy, and venereal disease. These are past uses, not proof that the treatments work. The source rates medicinal use low and lists no other uses.