July 30, 2022
Have you ever grown sunflowers with their tall stalks and bright, cheerful flowers?
Sunflowers (Helianthus) belong to the family Asteraceae. Yes, they look somewhat like asters. But the old name for the group is Compositae. This name tells us more about the flowers. Plants in this group are composed of two types of flowers in a head arrangement. The outer ring of Helianthus looks like bright yellow petals; these are the sterile ray flowers. The inner circle is composed of the darker disc flowers; these are the fertile flowers that produce the seeds.
There is great diversity within this group. The family Asteraceae has 24,000 species and worldwide distribution. The variation in ray and disk flowers is amazing. The variation in size of the flowers is also amazing—from the small fleabane, Erigeron, to the giant sunflower, Helianthus annuus.