From our perspective as Foxglove plants (Digitalis spp.), the pot is our entire world. Unlike our cousins in the wild who can send roots deep and wide in search of nutrients and moisture, our existence is confined by the container's walls. Therefore, the primary consideration must be our root architecture. We are primarily biennial, meaning we focus on vegetative growth (a low rosette of leaves) in our first year, and then send up our famous flowering spike in the second. This two-year cycle requires a root system that is both deep enough to anchor a tall, heavy flower spike (which can reach 6 feet or more) and extensive enough to support large, broad leaves. A pot that is too shallow will not provide adequate anchorage, risking toppling in a strong wind. We require a pot that accommodates a deep, strong taproot alongside a network of fibrous secondary roots.
For a single, healthy Foxglove, a pot with a minimum depth of 12 inches and a similar diameter is essential. This volume of soil provides sufficient space for our root system to develop properly over two years. A common mistake is to plant us in a pot that is just big enough for our initial small size; this leads to us becoming "root-bound." When our roots circle the inside of the pot, they become constricted and unable to effectively take up water and nutrients. This stunts our growth and can prevent the development of a robust flowering spike. For those of you wishing to create a more dramatic display, a larger container—perhaps 18 inches in diameter and depth—can accommodate two to three plants. However, you must ensure there is still adequate space for air circulation around the foliage to prevent fungal diseases. Crowding us too closely in a pot creates a damp, stagnant environment that is detrimental to our health.
The material of the pot directly influences the moisture and temperature of our root zone, which is critical to our well-being. We prefer consistently moist, well-drained soil; we do not tolerate "wet feet" (soggy roots), which quickly lead to fatal root rot.
Terracotta or Clay Pots: These are excellent choices for us. Their porous nature allows air to penetrate the soil and excess water to evaporate through the walls. This helps prevent waterlogging and keeps our roots oxygenated. The main drawback is that they can dry out very quickly in hot, sunny weather, requiring vigilant watering. The heavy weight of a large terracotta pot is also a benefit, providing stability against our tall flower spikes.
Glazed Ceramic or Plastic Pots: These materials are non-porous, meaning they retain moisture for much longer. While this can be an advantage in reducing watering frequency, it poses a significant risk of overwatering. If you choose these pots, you must be exceptionally careful with your watering schedule and ensure the drainage holes are large and unobstructed. Plastic pots are also lightweight, which may necessitate placing a heavy stone in the bottom to prevent tipping.
Fabric Grow Bags: An increasingly popular option, these bags provide excellent air circulation, which "air-prunes" our roots. This means when a root tip reaches the air-permeable fabric, it stops growing, preventing circling and encouraging a dense, healthy root system full of fine feeder roots. They also offer superb drainage.
Regardless of the size or material you choose, the single most important feature is adequate drainage. A pot without drainage holes is a death sentence for us. Standing water at the bottom of the pot will suffocate our roots and promote rot. Ensure there are several sizable holes in the bottom of the container. It is also good practice to add a layer of coarse material, such as broken pottery or gravel, at the bottom before adding potting mix to further improve water flow away from our root zone.
