Angiosperms: Dicotyledons

Asteraceae
Daisy Family

• Notes:

  Helianthus rigidus is similar to H. grosseserratus except the stem is often rough and usually not quite as tall. Leaves are smaller, more tapering at the base to a short leaf stalk, with smooth or small-toothed margins and rough hairs on both upper and lower surfaces. The disk flowers are purple, and the fillaries have stiff marginal hairs and are more blunt-tipped and closely appressed to each other. Flowering is from mid-August to early September, and fruiting begins in late August. H. rigidus is infrequent on dry and sandy prairies and even less frequent in more moist habitats.

  Hybrids between H. grosseserratus and H. rigidus are not uncommon. Gradations in stem and leaf roughness and leaf toothing are particularly apparent.

• Bibliography from Biodiversity Heritage Library
• Vascular Plants of Iowa