Foxglove's low-growing foliage is topped by 2- to 5-foot-tall flower spikes, depending on the variety. Foxgloves are biennials or short-lived perennials. Although individual plants may be short-lived, foxglove readily self-sows and multiplies. Foxglove leaves contain digitalis, a potent heart medicine, and are considered poisonous. Blooms in midsummer and adds elegance to a perennial border, woodland area, or shade garden.