Everything You Need to Know About Foxgloves
Brightly colored, bell-shaped foxglove flowers look just as good in the ground as they do in container gardens. What's more, they're easy for both amateur and expert gardeners to grow at home. "Foxgloves are versatile plants that add drama, color, and vertical interest to the garden," says Adam Dooling, curator of outdoor gardens and herbaceous collections at the New York Botanical Garden. "They can be used in a variety of settings, from conventional bedding-out, to mixed perennial borders, 'wild' plantings, and container displays."
But before you add the plants to your spring garden, it's important to understand their growing needs, blooming schedule, and—most critically—their toxicity. "Knowing their nature, and how to best utilize them, will reward the gardener sevenfold—sometimes with seedlings in the most unexpected of places," says Dooling. "This spontaneity is part of the joy of growing foxgloves."
What Makes Foxgloves Toxic
Foxglove plants contain digitoxin, a medicinal compound that affects the rhythm of the heart. "Digitoxin is similar to digitalis, a commonly used heart medication, and digitalis is actually derived from the foxglove plant," says Kelly Johnson-Arbor, M.D., medical toxicologist and co-medical director of the National Capital Poison Center. Digitalis works on cells in the heart—it's often prescribed to regulate the heart rhythms in patients with atrial fibrillation—but too much digitoxin can be fatal. "This medication has a very narrow therapeutic index, and small changes in dosing can result in significant toxicity," says Johnson-Arbor. "Ingestion of digitoxin from the foxglove plant can result in abnormal heart rhythms and irregular heartbeats, loss of consciousness, and death."
The toxin appears in the leaves, flowers, and all other parts of the plant, and isn't mitigated by steeping or cooking. "The leaves are similar in appearance to baby spinach and comfrey; people have experienced significant illness and death after mistaking foxglove for these two plants," says Johnson-Arbor. "The initial symptoms of foxglove and digitalis poisoning may involve nausea, vomiting, and seeing yellow halos around lighted objects. Interestingly, some people think that Vincent Van Gogh was prescribed digitalis prior to his death, and this is why many of his paintings have vivid yellow halos present."
Johnson-Arbor recommends several simple safety precautions: planting foxglove at a distance from any edible plants, so there's no chance of confusing it with salad greens, and keeping the growing plants or cut blooms out of reach of children and pets. "Touching the plant will not cause toxicity but eating it can result in significant toxicity or even death," she says. "The best way to avoid getting poisoned by foxglove is to not eat it. Instead, admire this beautiful plant from afar!"
Growing and Caring for Foxgloves
The Digitalis genus includes more than 20 types of plants and shrubs, but, says Dooling, "When people think of foxgloves, they are usually thinking about Digitalis purpurea, the common foxglove, native to Europe and found in most parts of the temperate world. The flowers are tubular, often speckled but sometimes clear, and bloom in shades of purple, rose, pink, apricot, yellow, white or bi-color." The flowers thrive in areas with full sun or part shade and prefer well-drained soil that's not too wet or too dry—so they are equally happy in containers or in ground plantings.
The plants grow well from seeds or cuttings—in shady spots, you may need to stake larger stalks—and will bloom for two to three months starting in late spring. "The foxgloves' bloom period from late spring to early summer means they will provide color to overlap between your spring bulbs and summer-blooming perennials," says Dooling. "They are a favorite of Lepidoptera—the order of moths and butterflies—so they will also add value to the wildlife in your garden. Foxgloves also make for stunning vertical elements when used in container displays, their need for drainage making them perfectly suitable for growing in pots."
Foxgloves: A Biennial Plant
Common foxgloves are biennial plants, which means that unlike perennials, which come back each year, and annuals, which last only a single season, the plant takes two years to fully flower before finishing its life cycle. "Most people misunderstand the nature of foxgloves, expecting them to behave as their perennial plants would and reliably bloom year after year," says Dooling. Look for your plant to grow "a rosette of foliage in its first season before developing tall spikes of large, bell-shaped flowers in the second season," says Dooling. "First year rosettes can be moved throughout the season easily, so you can enjoy their flowers the next season where you want them."
Between the first and second season, the plants need to spend four to six weeks at temperatures between 38 and 45 degrees to encourage new flowers—a process called vernalization. "Many outdoor garden conditions will provide this," says Dooling, "provided there is ample drainage and protection from winter damage." If you're hoping to grow foxgloves that mimic the dramatic versions at flower shows or botanical gardens, though, you'll need a controlled setting, like a greenhouse—or a specific cultivar. "In recent years, many new cultivars have entered the market that do not require vernalization, making them easier to grow—an amenable choice for both growers and the home gardener that does not have a range of greenhouses," says Dooling.