Foxglove beardtongue (Penstemon digitalis) is an herbaceous plant related to plantains. Penstemon digitalis means “finger-like” due to the plant’s flowers resemblance to the fingers of a gloved hand. Foxglove beardtongue is easily grown and often cultivated on roadsides for landscaping purposes.
I. Appearance and Characteristics
Penstemon digitalis (known by the common names foxglove beard-tongue, foxglove beardtongue, talus slope penstemon, and white beardtongue) is a species of flowering plant in the plantain family, Plantaginaceae. The flowers are white and are born in summer. It is native to eastern Canada and the eastern and southeastern United States. Penstemon digitalis is the most widespread species of Penstemon east of the Mississippi River.
The genus Penstemon is the largest in North America with 270 species. However, genome size was relatively unknown for the species, which can be important for taxonomy. Scientists estimated the genome size for 40% of the species in the genus using flow cytometry. Penstemon digitalis has one of the largest genomes of the genus Penstemon.
Penstemon digitalis is a glabrous 3 to 5 foot tall herbaceous plant with opposite, shiny green, simple leaves, on slender, purple stems. The leaves are up to 5 inches long. While upright, the stems average anywhere from 2 to 3 feet tall. The flowering panicle extends to almost one third of the plant’s height and has pairs of branches which repeat with two flowers multiple times. The pedicels are almost one fourth of an inch long and produce 1.25 inch long two-lipped tubular flowers over dark green foliage. The flowers have tiny white hairs on the outside of the tube. The plant has elliptic basal leaves and lance-shaped to oblong stem leaves.
The species was originally described as “Fox-Glove-Like Pentstemon” (sic) and the specific epithet digitalis is a direct reference to the foxglove genus Digitalis. The plant grows in moist, sandy soil in full sun in meadows, prairies, fields, wood margins, open woods and along railroad tracks. Its bloom period is from late spring to early summer. The plant is known to attract butterflies, bees, and birds such as hummingbirds. It tolerates deer browsing.
II. How to Grow and Care
Sunlight
This wildflower will perform best in full sun to light shade, ideally with at least six hours of direct sunlight per day. Your plants will display their most abundant blooming and well-developed overall form when grown in full sun. You can also grow beardtongue plants in light shade and they will better appreciate a bit of afternoon shade in warmer summer climates.
Climate and Temperature
Foxglove beardtongue is tolerant of most growing conditions throughout the eastern United States. It is a perennial in USDA Plant Hardiness Zones 3 through 8 and performs best in cooler to mild climates rather than persistently hot, excessively humid, or prolonged arid climates.
Watering
Foxglove beardtongue is highly adaptable, and once your plants are established, they shouldn’t need any supplemental watering. They will do well in dry to medium-moisture soil conditions. Avoid overwatering, as they are not tolerant of continually wet conditions.
Soil
The soil should be average quality and well drained. Soils rich in organic matter will allow your plants to become hearty and robust. Use some nutrient-rich soil amendments to particularly poor and sandy soils. Organic compost is a great choice to help boost nutrient-poor soils.
Fertilizing
Most native plants growing in their native regions typically don’t require extra fertilization. If you are growing in average-quality or organically rich soil, you shouldn’t need to add any extra fertilizers.
If your area has sandy or gravelly soil, you’ll want to boost the soil quality before planting these wildflowers. The best thing you can do to energize your native plants is to offer them a top layer of organic compost or biodegradable mulch that will slowly break down and release nutrients into the soil.
Propagation
Propagate by seed or by division of larger clumps. If you already have beardtongue growing in your yard, division will be the quickest method to create new plants.
If you don’t yet have it, you can easily start these plants from seed. Cultivars are best grown from division because seeds collected from cultivars won’t grow true to the parental type.
- Seed
Foxglove beardtongue seeds require cold stratification before they will germinate. The simplest way to do this is to direct sow your seeds in the fall and gently press them into the soil (don’t cover them because they need light to germinate). Try to make sure the soil stays moist during the winter months, and your seeds will germinate naturally in the spring when the weather starts to warm again.
If you want a little more control over the process, you can also start your seeds indoors. In mid-winter, place the seeds in moist sand and place them in your refrigerator for about two months to cold-stratify them. After the two months, sow the seeds in fresh potting soil or seed-starting soil. Place them on the soil surface and water them well. Keep the soil moist and warm, and within a few weeks, your seeds should start to sprout!
Continue to keep the seedlings moist until they have grown a bit larger and developed several true leaves. By this time, they should start developing a healthy root system and will become more tolerant of dry conditions. If you have problems with squirrels digging in your fresh soil, cover the seeds and seedlings with a critter cage to protect them from digging mammals and birds.
- Division
Mature clusters can be easily divided. In the spring or fall, dig out a clump of beardtongue, taking care to remove as much of the root material as possible. Using your hands, carefully separate the one larger cluster into two or more smaller clusters. Make sure each cluster has a few healthy stems and associated roots.
When you have separated your plants into multiple clusters, simply transplant each new cluster to the desired location. Try to work through this process quickly so the roots don’t spend too much time drying out. Pat fresh soil around each new transplant, and immediately after transplanting, water them all well to reduce transplant shock.
Transplanting
When you’re ready to transplant a potted beardtongue, plan for a cool, overcast day in the spring or fall, if possible. Identify the location where you’d like your plant to grow. Give them a place with plenty of sunlight and well-drained soil. You should also expect your plants to grow and spread over time, so allow at least one or two feet between each plant.
Dig a hole slightly larger than the pot in which the plant is currently growing. Carefully remove the plant from the pot and place it in the hole. Then, backfill around the roots with fresh soil and tamp down the soil around the plant.
Always water your newly transplanted plants well to help them settle into their new home. This is an excellent time to add a layer of mulch around your plants as well to help regulate soil moisture.
Pests and Diseases
Common Problems
Foxglove beardtongue is quite hardy and generally trouble-free. Poorly drained soil, however, can lead to root rot, and in humid growing conditions, you may encounter leaf spots.
- Root rot
Root rot is a potential problem, but only if your plants are growing in wet soil with poor drainage. It’s easy to prevent root rot by growing your plants in dry to medium-moisture, well-drained soil. But if your plant starts to develop root rot, it’s very difficult to save it.
Watch for wilting leaves, followed by soft, mushy leaves and stems. If you dig down, you will find the roots are also soft and mushy. The entire plant will die from an advanced case of root rot.
- Leaf spot
Leaf spot is generally caused by a bacterial or fungal infection of the plant leaves. Watch for brown, dead-looking spots on the leaves. A mild case of leaf spot will generally not kill your plants, but if you see several diseased-looking leaves, go ahead and prune these off to improve your plant’s appearance and prevent further spread. Don’t compost diseased or infected plant material because bacteria and fungus can overwinter in your compost and continue to spread.
Maintenance
Foxglove beardtongue is a very low-maintenance plant. When the plants go dormant for the winter, prune off the dead, dry, standing vegetation anytime during the winter to make room for fresh spring growth. Mulch around your plants to help preserve soil moisture, reduce weed competition, and boost soil nutrients.
If your plants spread beyond where you want them, do some periodic thinning to remove any unwanted extra growth. Deadhead spent flowers to encourage a prolonged blooming season or allow some seedheads to mature and collect your own seeds.
III. Uses and Benefits
- Ornamental uses
Foxglove beardtongue is a popular plant in summer flower gardens prized for showy blooms that attract pollinators. Commonly grown behind border plants, the tall flower spikes make a statement when they are in bloom. Foxglove beardtongue is often grown with delphinium to create a flowering backdrop, or mixed with shorter perennials like coneflowers and salvias to showcase the plants’ contrasting heights.
- Wildlife uses
Foxglove beardtongue plants have excellent wildlife value. While they are not generally bothered by deer or rabbits, they are very attractive to pollinators. Bees especially love to crawl into the flowers to gather the nectar.
You will see a variety of other pollinators and even hummingbirds visiting the tubular flowers. This is a beautiful plant to add to your pollinator-friendly landscape, and it’s sure to bring in plenty of pollinator activity.
Find Where to Buy the Best Foxglove Beardtongue (Penstemon digitalis)
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