On 29 August I posed the question “How do wild senna flowers become shiny green bean pods?” Last week I decided to find out.
Wild senna (Senna hebecarpa) flowers grow in bunches on a tall stem.
Each flower holds the secret to the bean. In the closeup below you see irregular yellow petals, stamens with brown anthers, and a tiny green stem with fuzzy white edges — the pistil. Instead of a single ovary at the base of the pistil there’s apparently a row of ovaries inside.
When the flower is fertilized, the yellow petals fall off. The stamens and pistil remain.
As the fuzzy green pistil grows the anthers fall off
Though still fuzzy, the former pistil begins to look like a bean pod.
The remaining twigs fall off, the bean pods lose their fuzz and Ta Dah!
The secret is that row of ovaries.
(photos by Kate St. John)