Most foxgloves are biennial flowers; they reseed and return like an annual. If you allow the seed to mature and drop, you continue having flowers. The first year, a basal clump of leaves develops; a flowering stalk develops in the second year. In warmer regions, foxglove may return as a perennial. Nurseries may carry some foxglove varieties, but are more choices if you purchase seeds.
The majority of hybrid foxgloves are developed from Digitalis purpurea this species. Common foxglove is native to Europe, but has naturalised in many parts of the United States. It often appears in clearings, waste areas and along roadsides. The flower is lavender-pink with white spots and dark purple specks. D. purpurea is hardy to U.S. Department of Agriculture Plant Hardiness Zone 4.
Hybrid Digitalis Purpurea
There are many different colours of hybrid foxgloves. D. purpurea "Apricot Beauty" has creamy-pink flowers. The Camelot series comes in white, pink, lavender and apricot. The distinguishing feature is the dark speckles inside the flowers. The Polka Dot series of foxglove boast white spots inside each flower. A new variety called Polka Dot Polly is a much deeper shade of pink. "Alba is a pure white foxglove with no spots at all. Most foxgloves have 3 to 4 foot tall flower spikes. There is a dwarf variety called Virtuosa Rose. It is only 2 to 3 feet tall and is a medium-pink colour. All hybrid D. purpurea plants are hardy to USDA zone 4.
D. grandiflora is a yellow foxglove. It is of European origin and naturalised throughout the Northeast portion of the United States. It is sometimes called the large yellow foxglove because of the size of its individual flowers. It is shorter than D. purpurea and reaches 2 to 3 feet tall. Often dubbed the perennial foxglove, it returns and flowers each summer. Big yellow foxglove is hardy to USDA zone 3. Until recently, hybrid forms were not available. Now there is a dwarf variety called Carillon, which reaches 12 to 16 inches. Carillon is hardy to zone 4.
Another promising foxglove is D. mertonensis. It was developed by crossing D. purpurea and D. grandiflora. This foxglove is a short-lived perennial but returns from seed. There is one hybrid variety called Strawberry. It has coppery-pink flowers and is 2 to 3 feet tall. Strawberry foxglove is hardy to USDA zone 3.
Facts About Digitalis
All parts of foxglove are poisonous if ingested. Digitoxin is extracted from D. purpurea and used to treat heart ailments. Foxglove plants are also toxic to livestock and should not be allowed to naturalise in pastures. Growing foxgloves as an ornamental plant in the home garden should not pose any problems.