Known by various names such as witches' gloves, fairy's gloves or fairy thimbles, foxglove (Digitalis purpurea) is easily recognized by spikes of tube-shaped blooms ranging from deep purple to pale lilac, yellow and mauve. The striking blooms, which reach heights of 2 to 8 feet depending on the variety, grow from clumps of fuzzy, grayish-green leaves. A cool-weather plant, foxglove is perennial in U.S. Department of Agriculture plant hardiness zones 4 through 8.
Water and Fertilizer
Foxglove is an undemanding plant that thrives with a moderate level of care. Water the plant during warm weather when rainfall is less than 1 inch per week. Soak the soil to a depth of about 6 inches. To prevent diseases, water foxglove at the base of the plant and keep the leaves as dry as possible, then let the top of the soil dry before watering again. Foxglove doesn't require frequent feeding and too much fertilizer results in tall, floppy plants with lush foliage but few blooms. Apply about 3 tablespoons of a 5-10-5 fertilizer in spring. If growth appears weak or the foliage is pale green, provide additional feedings in midsummer and late summer.
Foxglove is susceptible to diseases such as crown rot, wilt and leaf spot. However, diseases are usually preventable by proper care and maintenance. Foxglove is a drought-tolerant plant that doesn't perform well in soggy soil or crowded conditions that prevent ample air circulation. Although foxglove is highly pest resistant, it is particularly attractive to slugs. Slugs are easily removed by hand if the infestation is light. For a heavy infestation, use a commercial slug bait, which is available in both regular and nontoxic varieties. As a general rule, slug bait is best applied lightly at a rate of 1 teaspoon per square yard. Always read the container for specific instructions.
Trim blooms when about three-fourths of the spike has wilted to keep the plant neat and stimulate the plant to produce more blooms. Cut the spikes down to the clump of leaves after blooming ends in late summer. Spread 2 to 4 inches of mulch around the plant in autumn to protect the roots during the winter. However, don't mulch until the ground freezes because mulching while the soil is still warm often promotes crown rot and other diseases. Remove the mulch in spring and apply a 1- to 2-inch layer of mulch or compost to conserve water and control weeds. Don't mulch heavily because a thick layer of mulch promotes disease and invites slugs.
Digitalis, an important cardiovascular medication used to treat heart failure, is made from compounds extracted from the foxglove plant. Additionally, other medications are made from steroids derived from foxglove. While the substances are medicinally advantageous, the plant is highly toxic and overdoses may be fatal. Symptoms include headache, vomiting, convulsions and irregular heartbeat.