Pictured above: Rayless sunflower (Helianthus radula) by Eleanor Dietrich. Click on terms for botanical definitions. View post as a PDF.
Rayless sunflower (Helianthus radula) is a unique member of the Helianthus or sunflower genus. It occurs naturally in sandy uplands, along moist to dry roadsides, and in seasonally wet savannahs and pine flatwoods. It typically blooms late spring into early fall, attracting a variety of butterflies and other pollinators.
Like most sunflowers, its flowerhead includes a compact but relatively large center composed of many small, maroon to dull brown disk florets. But unlike its relatives, its ray florets are almost entirely absent, hence the common name “rayless.” (Some specimens do produce a few small, yellow ray florets.) Each plant typically produces a single flowerhead. Basal leaves are thick and rounded with rough, hairy surfaces. Stem leaves are few, elliptic to ovate and hairy, becoming reduced in size as they ascend the stem. They are oppositely arranged. Stems are also hairy.
The genus name Helianthus is from the Greek helios, or “sun,” and anthos, or “flower.” The species epithet radula is from the Latin radula, meaning “scraper,” referring to the roughness of the leaf surfaces.
Family: Asteraceae (Composite or daisy family)
Native range: Panhandle, most of Central and North Florida, and Collier County
To see where natural populations of rayless sunflower have been vouchered, visit florida.plantatlas.usf.edu.
Hardiness: Zones 8A–9B
Soil: Seasonally moist to dry, sandy soils
Exposure: Full sun
Growth habit: 1–2′ tall
Garden tips: Appreciate Rayless sunflower for its unusual flowerheads and large basal leaves. It is a great addition to a home pollinator garden, as it easily adapts to a variety of conditions and will attract butterflies as well as other pollinators. It does best in open, sunny areas. Plant with a mix of Chalky bluestem or Muhlygrass for a striking display.
Rayless sunflower seeds are sometimes available through the Florida Wildflower Cooperative. Plants are often available at nurseries that specialize in native plants. Visit PlantRealFlorida.org to find a native nursery in your area.
For more information on other Helianthus species, see these resources: