From our perspective as Digitalis plants, the primary obstacle to a happy life indoors is our fundamental biological need for a winter dormancy period. We are biennials or short-lived perennials, meaning our life cycle is intrinsically tied to the seasons. We spend our first year growing a leafy rosette, then we flower, set seed, and often die in the second year. To successfully initiate flowering, we require a period of cold stratification—a sustained exposure to winter's chill. The consistent, warm temperatures of a typical human dwelling (65-75°F or 18-24°C) prevent this crucial process. Without this cold trigger, we may persist as a foliage plant but will likely never send up our iconic flower spike, which is, from our point of view, our entire reason for being.
Our growth habit and flowering process are exceptionally energy-intensive. Outdoors, we thrive in full sun to partial shade, meaning we are adapted to absorb many hours of direct, bright light each day. Even the sunniest south-facing window indoors filters and reduces light intensity significantly. To photosynthesize effectively and produce the energy required to build our large flower spire, we need more photons than a windowsill can typically provide. This would lead to etiolation—where we become leggy, weak, and pale as we stretch desperately for more light. Without supplemental, high-intensity grow lights positioned very close to our foliage for 12-16 hours daily, we will simply not thrive.
Please consider our size and form. We are not a compact, low-growing plant. In our first year, we form a sizable rosette of large, fuzzy leaves that can easily span over a foot (30 cm) wide. In our second year, our flower spike erupts from the center, reaching heights of 2 to 5 feet (0.6 to 1.5 meters) or even more, depending on the cultivar. We require a deep and spacious pot to accommodate our substantial taproot, and the tall, heavy flower spike will need staking indoors to prevent it from toppling over. Our structure is simply not suited to the confined space of most indoor settings.
The indoor environment presents other subtle but critical challenges. We prefer cool, moist roots and good air circulation. Indoor heating creates very dry air which can stress our leaves and make us more susceptible to spider mites, a common pest in dry conditions. Furthermore, while we enjoy moist soil, we are extremely susceptible to crown rot if water sits on our foliage or if the potting medium remains soggy. Achieving the perfect balance of humidity, moisture, and airflow is far more complex indoors than in our natural outdoor habitat where rain and wind naturally manage these factors.
Ultimately, our genetics are coded for a life outdoors. We are wildflowers, meadow plants, and woodland edge dwellers. While the intention to care for us indoors is appreciated, forcing us to live inside goes against our very nature. The conditions we require to complete our life cycle—deep cold, abundant direct light, ample vertical space, and natural airflow—are nearly impossible to replicate perfectly in a human home. It is a constant struggle to adapt. You may keep us alive for a season, but we will not truly flourish, and we will almost certainly never achieve our magnificent reproductive goal: to flower.
