Beardtongue (Penstemon digitalis 'Onyx and Pearls')

Overview

Penstemon digitalis ‘Onyx and Pearls’ is a striking herbaceous perennial that commands attention in the garden, often referred to simply as Beardtongue. This cultivar stands out due to its remarkable, nearly black-purple foliage that perfectly contrasts with its later spring blooms. The upright habit and dependable performance make this selection a workhorse in mixed borders and native plantings.

As a vigorous selection of foxglove beardtongue, Penstemon digitalis ‘Onyx and Pearls’ thrives in full sun conditions, which are essential for maintaining that rich, dark leaf coloration. It offers low maintenance once established, tolerating drought and even clay soils, proving itself remarkably adaptable across USDA Zones 3 through 8. Gardeners value this plant for its visual drama and its ability to sustain interest from spring bloom well into the growing season.

Hummingbirds and butterflies actively seek out the pale purple to nearly white flowers typical of this fine Beardtongue. Its structure provides excellent vertical accent, making it a superior choice for contemporary landscapes seeking year-round structure and seasonal floral impact.

Fast Facts

• Plant Family: Plantaginaceae
• Plant Type: Herbaceous perennial
• Hardiness Zones: USDA Zones 3-8
• Size at Maturity:
  • Height: 3-3.5 ft
  • Spread: 3-3.5 ft
• Bloom Time: April to June
• Bloom Description: Pale purple to nearly white
• Sun Exposure: Full sun
• Water Needs: Dry to medium
• Maintenance Level: Low

How to Grow

The best time to plant Penstemon digitalis ‘Onyx and Pearls’ is during the spring or fall when temperatures are moderate. Ensure the chosen location provides full sun exposure; this intensity is crucial for promoting the deep purple pigmentation characteristic of this cultivar. Soil should generally be average, benefiting from good drainage, although Beardtongue shows tolerance for clay soils.

Water newly planted specimens regularly to establish a strong root system. Once mature, this Penstemon is notably drought tolerant, thriving on dry to medium moisture levels; avoid overly wet, poorly drained conditions, especially in winter, as this invites root rot. Minimal fertilization is usually required; too much rich organic matter can lead to floppier growth and reduced flower production.

Maintenance is straightforward. Deadheading spent flower stalks is optional but can encourage a tidier appearance for this Beardtongue. In early spring, cut back any old or damaged stems. Because this perennial can spread somewhat aggressively, occasional division may be necessary every few years to manage clump size and maintain neighborly relations in the border.

Landscape Uses

Penstemon digitalis ‘Onyx and Pearls’ excels when used for mass planting in sunny borders, creating dramatic drifts against lighter perennials. The deeply pigmented foliage of this Beardtongue serves as an exceptional dark backdrop, highlighting the bright flowers of adjacent plants. It is highly recommended for rain gardens due to its tolerance for both dry spells and periods of inundation once established, fulfilling the suggested use criteria perfectly.

This plant integrates seamlessly into wild gardens or naturalized areas where its upright structure provides necessary height without becoming unruly. Furthermore, due to the quality of its blooms, Penstemon digitalis ‘Onyx and Pearls’ is evaluated as excellent for fresh cut flower arrangements when harvested in peak condition. Consider pairing this dark Beardtongue with silver foliage or vivid yellow flowers for maximum chromatic contrast.

Standout Features

Flower Qualities

• Showy
• Good Cut

Noteworthy Characteristics

Penstemon digitalis, commonly called foxglove beardtongue or tall white beardtongue, is a clump-forming, Missouri-native perennial which typically grows 3-5’ tall and occurs in prairies, fields, wood margins, open woods and along railroad tracks. Features white, two-lipped, tubular flowers (to 1.25” long) borne in panicles atop erect, rigid stems. The common names of this species refer to the appearance of its flowers and growth habit, particularly the hairy sterile stamen that earns Penstemons the name beardtongues. ‘Onyx and Pearls’ is specifically noted as a cold-hardy, dark-leaved selection of foxglove beardtongue that features pale purple to nearly white blooms on upright flowering stalks.

Tolerances

• Deer
• Drought
• Clay Soil
• Dry Soil

Potential Problems

Root rot stands out as a primary concern for Penstemon digitalis ‘Onyx and Pearls’, especially if planted in heavy, perpetually wet soil where drainage is poor. To prevent this, ensure excellent soil aeration before planting. Leaf spots are occasional cosmetic issues but rarely threaten the plant’s survival when conditions are favorable. Gardeners should monitor its spread; this Beardtongue does have the potential to spread somewhat aggressively in ideal garden settings, requiring division to maintain borders. Deer tend to avoid this plant, offering it protection in wildlife-rich areas.

Frequently Asked Questions

What hardiness zones is Beardtongue suitable for?

Penstemon digitalis ‘Onyx and Pearls’ thrives across a wide range, suited for USDA Zones 3 through 8.

How large does Penstemon digitalis ‘Onyx and Pearls’ grow?

This perennial typically reaches heights between 3 and 3.5 feet, with a similar spread of 3 to 3.5 feet at maturity.

What sun exposure does Penstemon digitalis ‘Onyx and Pearls’ need?

This plant requires full sun exposure for optimal growth and to ensure the dark purple foliage develops its characteristic rich coloration.

When does Beardtongue bloom?

You can expect blooms on the Penstemon digitalis ‘Onyx and Pearls’ from April to June, displaying attractive pale purple to nearly white flowers.

Conclusion

Penstemon digitalis ‘Onyx and Pearls’ delivers significant ornamental impact through its dramatic dark foliage and its attractive, pollinator-friendly floral display. This resilient variety of Beardtongue offers low-maintenance gardening combined with high visual reward, suitable for naturalized settings or structured borders alike. Before planting, confirm your site receives adequate sun and confirm its hardiness zone compatibility for best results with your Penstemon display.

Companion Planting Strategies

Companion planting near Penstemon digitalis ‘Onyx and Pearls’ should focus on maximizing the striking contrast offered by its dark leaves. Silver-leaved plants, such as certain Lamb’s Ears (Stachys) or artemisias, provide a beautiful, cooling contrast directly adjacent to the dark foliage. For summer color after the Beardtongue finishes blooming, consider pairing it with plants that appreciate similar dry-to-medium moisture conditions, like Coneflowers (Echinacea) or various Sedums. Since this Penstemon tolerates clay soil, selecting drought-tolerant companions that can handle similar soil profiles ensures all neighbors thrive without requiring excessive adjustments to the watering schedule.

Designing with Dark Foliage

The deep purple architecture of Penstemon digitalis ‘Onyx and Pearls’ makes it a powerful tool in modern garden design, functioning almost as a foliage plant during the non-blooming season. Use it to ground brighter-colored perennials, providing necessary visual weight that prevents the entire border from looking washed out in bright summer light. When placed near an edge, the dark leaves draw the eye inward, acting as a visual anchor. Consider using it near paths or entryways where the deep color can be appreciated up close, especially recognizing its value in native plant gardens.