During the flowers’ three-times-a-week inspection, an Edmonds city parks staffer noticed something off. Small flecks of gray mold peppered most of the petals on the red and yellow petunias.

"To collect coneflower seeds by hand, wait until the flower heads turn brown and the petals fall off," she says. "Then, grasp the base of the flower head and give it a firm shake over a paper bag ...