The plantain family (Plantaginaceae) gifts us with some wonderful ornamental flowering plants, including snapdragons, foxglove, and the valuable Penstemon genus, which contains more than 250 beardtongue species ready to grow in your garden. Penstemon plants are herbaceous perennials that feature lance-shaped foliage and spikes of tubular flowers. Flower colors include pink, red, white, purple, and (rarely) yellow. The nickname "beardtongue" refers to the pollen-free stamen that protrudes from the flower, resembling a bearded iris in this aspect. This perennial is easy to grow from seeds planted in spring to early summer. It's somewhat slow to start and needs 10 to 21 days to germinate.
|Plant Type||Herbaceous, perennial|
|Mature Size||6 in. to 8 ft. tall and 8 to 20 in. wide|
|Soil pH||Neutral to acidic|
|Bloom Time||Spring, summer|
|Flower Color||Purple, blue, orange, red, yellow, pink, white|
|Native Area||North America|
Beardtongue plants typically bloom in early summer, filling that gap between the end of spring bulbs and the maturing of summer flowers like coneflowers, yarrow, and coreopsis. Most penstemons are 1 to 3 feet tall, but Palmer’s penstemon can grow up to 6 feet, giving you options for the middle and back of the border. Keep the penstemon flowerbed weeded regularly. A 3-inch layer of organic mulch can help to control weeds, and rock mulch is also a suitable choice. You can cut the spent flower stems back after blooming to help plants look tidy. Penstemons don’t compete well with other plants, so give them plenty of space in the garden.
Plant your beardtongue in an area that receives full sun. Adequate sun exposure helps the tall stalks stay upright and not droop.
The soil for beardtongue must drain very well. These plants are prairie natives and prefer rocky or sandy lean soil types rather than rich garden loam. It’s fine to amend the soil with compost to achieve proper tilth but avoid manure applications.
Penstemons tolerate drought, but 1 inch of water per week in the summer will keep plants vigorous and promote better blooming.
Temperature and Humidity
Gardeners in USDA growing zones 3 to 9 have the option to try penstemons, although some varieties may only be hardy to zones 4 or 5. It can thrive in a range of humidity conditions.
Feed beardtongue plants once a year with organic fertilizer, applied in the fall. Feeding these flowers with conventional bloom-boosting formulas can promote too much growth and can shorten the life of the plants.
Types of Penstemon
- 'Dark Towers' is similar to Husker Red, but with pale pink flowers and darker foliage.
- 'Elfin Pink' is a good rock garden plant, topping out just shy of 12 inches.
- 'Husker Red' is perhaps the most well-known variety, due to being named perennial plant of the year in 1996; it features reddish-purple foliage and white flowers.
- 'Jingle Bells' has reddish-orange flowers that are beacons to hummingbirds.
- 'Piña Colada', a series of cultivars, features blue, rose, or white flowers on compact plants.
- 'Red Riding Hood' has red flowers and an upright growth habit.
Beardtongue doesn't need pruning but can benefit from cutting off the spent flowers down to the stem to encourage new blooms.
Since a majority of beardtongue varieties are short-lived perennials, growing them from seed is the best and easiest method of propagation.
How to Grow Beardtongue From Seeds
Penstemons are easy to start from seed. Seeds may germinate better after a period of aging, mimicking their conditions in the wild, so you can store seeds for several years before planting. If you sow the seeds in the garden, do so in autumn, to allow a natural stratification period. Alternatively, you can stratify the seeds in the refrigerator for three months if you plan to start them indoors. If you purchase seeds, be sure to check the growing zone, as tender varieties like the ‘Tubular Bells’ series are often sold alongside the hardy perennial types.
Don't bother to cut away any foliage during the winter, as this can help protect the plant. A thick layer of fallen leaves can provide plenty of additional protection.
Common Pests and Plant Diseases
Penstemons don't suffer from too many insect problems, but slugs and snails may snack on leaves, especially in damp or shady areas. Sprinkle diatomaceous earth around plants to deter gnawing insects and set out beer traps to catch any stragglers.
Penstemon plants are usually disease-free when given the proper culture of full sun and good drainage. Gardeners with heavy clay may lose plants to root rot, especially in areas with heavy snow that experience a long spring thaw. In Southern gardens, plants that don't have adequate soil drainage or are planted too closely together may succumb to powdery mildew or Southern blight, a fungal disease also known as white mold. Fungicide sprays treat symptoms but not the cause, so lighten your heavy soils with compost, or plant penstemons in raised beds to add air circulation for the roots.
How to Get Beardtongue to Bloom
When placed in the garden, give the plants plenty of room, about 1 to 3 feet apart. Add in a little compost if your soil is lacking in nutrients. Water the plants at least once a week when they're young and use generous mulch to cut down on weeds that compete for nutrients and light. Mulch will also help protect the roots from cold snaps.
Can beardtongue grow indoors?
Given the need for full sun and a tall, fast-growing habit, these plants don't do well indoors.
What are alternatives to beardtongue?
There are many alternative plants of the same family that provide a slightly different look and various vibrant colors. Some of these include Stapleford Gem, Garnet, Apple Blossom, and Firebird.
What is the difference between foxglove and beardtongue?
Beardtongue and foxglove look quite similar. Beardtongue is of the genus Penstemon, while foxglove is of the genus Digitalis. While beardtongue is quite safe, foxglove is quite toxic.
Penstemon. University of California Cooperative Extension.
Powdery Mildew. The University of Arizona Cooperative Extension.