You know it’s showtime when umbrellas are shading dahlias in the garden. Umbrellas protect the American tuberous-rooted plants so their blooms don’t fade in the hot sun or get damaged by heavy rain.

Dahlias are delightful additions to the garden because they keep on giving. “Dahlias are the ‘love flower,’ because the more you cut them and give them away, the more flowers they produce,” says Becky ...