Helianthus petiolaris aka Prairie Sunflower

Helianthus petiolaris belongs to the Asteraceae family. Its names include prairie sunflower, plains sunflower, and lesser sunflower. Its native range spans Canada to northern Mexico. It grows in temperate zones, where the climate is mild. It lives on dry prairies and sandy ground. It also grows on dunes, roadsides, and disturbed sites. This annual lives for one year. It can form broad stands on open ground.

Plants reach about 5 feet (1.5 metres) tall. They spread about 3 feet (0.9 metres) wide. They grow at a moderate rate. The leaves and flower heads feel rough and resinous. Flowers bloom from July to September. Each has both male and female organs. Bees and flies pollinate the flowers. Other insects visit them too. The small fruits have the name cypselae. They hold seeds that people can eat. Ripe fruits drop soon after they mature. This makes them hard to gather.

Give this plant full sun and soil that drains well. It grows in sand or loam, even with few nutrients. Loose soil with gravel suits it too. It accepts slightly acid, neutral, or slightly alkaline soil. Soil can be dry or moist. But rich, wet soil does not suit it well. Plants cope with heat and drought. Bare ground or sparse plant cover helps seedlings take hold. Dense growth of plants that live for years can hinder them. PFAF lists USDA zones 3–10 and a UK zone of 4. Sow seeds outside in mid-spring. You can start them under glass before then.

This plant suits garden beds and helps restore disturbed ground. Its roots help hold loose sand in place. Dead annual stems add organic matter to soil. Flowers feed insects, including after summer rain. Birds and small mammals eat the seeds. Dense stands give wild animals shelter for a short time. They can help prepare bare sites for plants that live longer. But heavy self-seeding can cause problems in small spaces. Thick stands may compete with crops. They may also compete with young plants grown to restore sites.

Only mature seeds have a well-documented use as food. You can roast them or grind them into meal. Small kernels and shells that resist removal make this slow work. Large stands yield more useful harvests than single plants. Clean, mature seeds are safe in most cases. People with sunflower allergies are an exception. Remove hairs and shell pieces before you eat them. Avoid seeds from polluted sites or soil exposed to herbicides. Do not assume you can eat leaves or flower heads. Traditional uses include leaf powder as dressings for sores and swellings.