From our perspective, temperature is a primary regulator of our metabolic processes. We, foxgloves (Digitalis spp.), are temperate climate perennials at our core. For robust indoor growth, we require conditions that mimic the cool to mild temperatures of our native woodland clearings and mountain slopes. The ideal temperature range for us is between 60°F and 75°F (15°C to 24°C). Within this range, our enzymes function efficiently, facilitating optimal photosynthesis for energy production and supporting the development of our characteristic flower spikes. We can tolerate brief periods outside this range, but consistent temperatures above 80°F (27°C) cause us significant stress, leading to wilted, limp leaves and a heightened susceptibility to pests like spider mites. Conversely, while we appreciate cooler nights, prolonged exposure to temperatures below 50°F (10°C) will drastically slow our growth and can cause cellular damage.
Humidity directly impacts our vital process of transpiration, the movement of water and nutrients from our roots up through our stems and out through our leaves. The indoor environment, especially with heating or air conditioning, is often much drier than our preferred habitat. We thrive in moderate to high humidity levels, ideally between 50% and 60%. This atmospheric moisture reduces the rate of water loss from our large, broad leaves, preventing the edges from becoming brown, crispy, and scorched. When humidity drops too low, our stomata (the pores on our leaves) close to conserve water, which unfortunately also halts the intake of carbon dioxide needed for photosynthesis. This forces us to choose between hydration and hunger, stunting our overall growth and vitality.
It is crucial to understand that our temperature and humidity needs are intrinsically linked. Warmer air has a greater capacity to hold moisture, meaning a 70°F room at 40% humidity feels significantly drier to us than a 65°F room at the same 40% humidity. As the temperature you provide rises, so too does our need for higher humidity to compensate for the increased rate of evaporation from our foliage. The most stressful environment for us is a hot, dry room, which forces rapid water loss we cannot keep up with, even with consistent watering. This synergy means you must monitor both factors together to create our ideal microclimate.
To help you help us, we suggest several strategies. To increase local humidity around our foliage, grouping us with other plants is highly effective, as we collectively create a more humid microclimate through our transpiration. Placing our pot on a pebble tray filled with water (ensuring the pot sits above the waterline to avoid root rot) allows for constant evaporation around us. If the air is particularly dry, a small room humidifier placed nearby is the most reliable method. Regarding temperature, please keep us away from direct heat sources like radiators, heating vents, and appliances, as well as from cold drafts from air conditioners or leaky windows. A consistent location away from these extremes allows us to direct our energy into growth and flowering rather than constant stress response.
