Dahlia — 23 species

Dahlias are tender tuberous perennials native to Mexico, delivering bold blooms from midsummer through first frost in forms ranging from compact pompons to giant dinner-plate varieties like Bishop of Llandaff. They demand full sun — a minimum of eight hours daily — and deep, infrequent watering three to four times per week once plants are established and at least six inches tall; avoid watering dormant tubers to prevent rot. All dahlias are toxic to cats and dogs according to the ASPCA, causing mild gastrointestinal signs and possible dermatitis.