The common foxglove, Digitalis purpurea, is typically a biennial plant, meaning its life cycle spans two years. This distinctive garden ornamental is known for its tall, spiky flower stalks covered in tubular, bell-shaped blossoms, often in shades of purple, pink, or white. Understanding its two-year growth pattern is important for successful cultivation.
Understanding the Biennial Cycle
A biennial plant is defined by a life cycle that begins and ends over the course of two growing seasons. The foxglove uses its first year solely for vegetative growth and energy storage. During this initial phase, the plant develops a low, compact cluster of large leaves known as a basal rosette, which remains close to the ground.
This rosette of hairy, prominently veined leaves absorbs sunlight, storing the necessary carbohydrates to survive the winter. The first year’s growth focuses entirely on establishing a robust root system and accumulating energy reserves for the following season. The plant remains in this low-lying, non-flowering state until the cold period signals the next stage of development.
In the second year, the foxglove bolts, sending up a single, towering flower stalk from the center of the basal rosette. This stalk, which can reach heights of three to five feet, is densely packed with numerous pendulous, tubular flowers. The plant is monocarpic, meaning it flowers once, sets seed, and subsequently dies. After the seeds mature and are dispersed, the entire plant withers away.
Cultivating Biennial Foxgloves
Because the common foxglove dies after flowering in its second year, gardeners must ensure a continuous display of blooms annually. The primary method is allowing the plant to naturally self-seed. A single foxglove can produce millions of tiny seeds, which are easily scattered by wind and germinate readily in favorable conditions.
When the second-year flowers fade, allowing the seed capsules to dry and split open ensures new first-year rosettes establish themselves in the late summer or fall. These seedlings will then overwinter and bloom the following year, creating a staggered, perpetual cycle. To manage the plant population, cut down most spent flower spikes while leaving only one or two to mature and disperse seeds.
Alternatively, gardeners can manually sow seeds in late summer or fall to ensure a controlled supply of first-year plants for the next season’s blooms. Since the seeds require light to germinate, scatter them on the soil surface and do not cover them. Staggering the planting of young plants or seeds over two years guarantees that both first-year rosettes and second-year flowering spikes are present simultaneously.
Perennial and Annual Varieties
While Digitalis purpurea is the archetypal biennial, the genus Digitalis includes species with different life spans. Some species are true perennials, meaning they bloom year after year from the same rootstock. Notable examples of perennial foxgloves include Digitalis grandiflora, known as the yellow foxglove, and Digitalis ferruginea, or the rusty foxglove.
These perennial types tend to be shorter-lived than other perennial flowers, lasting perhaps three to five years, but they do not die after their first flowering. Additionally, some modern cultivars and hybrids, such as the ‘Camelot’ or ‘Dalmatian’ series, have been bred to bloom in their first year from seed. These first-year flowering types are often treated as annuals, especially in regions with longer growing seasons, though they are technically biennials that skip the usual first-year rosette phase.