A cosmos bloom is less a single flower than a gathering designed to be seen. Pink rays spread around a golden center, while a slender stem lifts the display above finely divided foliage. The effect is delicate. Its reproductive machinery is anything but simple.
The apparent simplicity is the trick. Each bloom is a composite flower head, or capitulum, made up of many florets. Around the edge sit ray florets, whose broad, petal-like structures form a conspicuous display. In the center are disk florets, small tubular flowers that offer pollen and nectar to visiting insects. The arrangement concentrates rewards. A bee or other pollinator can move among several disk florets without flying to a separate plant, gathering food while brushing against reproductive structures that place pollen on its body.
The crowded center makes a persuasive advertisement, but attraction is only part of the bargain. When an insect carries pollen from one cosmos plant to another, it can help fertilize the flowers and enable seed production. Not every visit achieves that exchange, and the insects drawn to a bloom vary with local conditions. Still, a broad display and a cluster of rewards give the plant more opportunities than its modest outline might suggest. Above the feathery leaves, the pink circle holds its quiet multitude.
