To the delight of butterflies, honeybees, and hummingbirds, velvet purply-blue flowers on 1-foot stalks top this 4-foot-tall, nonhardy sage from June until frost. Indigo Spires salvia (Salvia 'Indigo Spires') is a chance hybrid of Salvia longispicata and Salvia farinacea; it was discovered by staff at the Huntington Botanical Gardens in 1979.