

How to Grow and Care for Penstemon Plants: A Complete Guide
Penstemon, commonly known as beardtongue, is a stunning perennial prized for its tubular, nectar-rich flowers and long blooming period. These vibrant plants attract bees, butterflies, and hummingbirds, making them an excellent choice for wildlife-friendly gardens.
Known for their hardiness and drought tolerance, penstemons thrive in well-drained soils and provide colour from late spring to autumn. Whether planted in borders, rock gardens, or containers, they bring a striking, natural elegance to any outdoor space.
This guide will cover everything you need to know about growing and caring for penstemon plants, including planting techniques, pruning, propagation, pest control, and the best varieties for different garden settings.
Understanding the Different Types of Penstemon Plants
With over 250 species, penstemons come in a variety of sizes, colours, and growth habits. Below are some of the most popular types cultivated in gardens.
1. Border Penstemons (Large-Flowered Hybrids)
Border penstemons are the most common garden varieties, known for their large, showy flowers and extended flowering season.
Popular Border Penstemon Varieties
- ‘Pensham Plum Jerkum’ – A deep purple variety with a white throat.
- ‘Sour Grapes’ – Features iridescent purple-blue blooms.
- ‘Firebird’ – Bright red flowers ideal for pollinator gardens.
- ‘Hewell’s Pink’ – A soft pink variety that blends well with cottage garden plantings.
2. Alpine & Rock Garden Penstemons
These compact varieties thrive in well-drained, rocky soils and are perfect for alpine gardens or container displays.
Popular Alpine Penstemon Varieties
- ‘Penstemon rupicola’ – A creeping species with bright pink flowers.
- ‘Penstemon davidsonii’ – A low-growing purple-flowered variety.
3. Native and Wild Penstemons
These drought-tolerant species are often used in naturalistic plantings and wildflower meadows.
Popular Native Penstemon Varieties
- ‘Rocky Mountain Penstemon’ (Penstemon strictus) – Deep blue-purple flowers, highly drought-resistant.
- ‘Foxglove Penstemon’ (Penstemon digitalis) – A tall, white-flowered species native to North America.
- ‘Beardtongue’ (Penstemon barbatus) – A classic red-flowered variety that attracts hummingbirds.
Penstemon in Garden Design
Penstemons are versatile and work well in a variety of garden settings.
- Cottage Gardens: Pair with roses, lavender, and salvia for a traditional English garden feel.
- Wildlife Gardens: Their tubular flowers attract bees, butterflies, and hummingbirds.
- Drought-Tolerant Landscapes: Mix with sedums, echinacea, and ornamental grasses.
- Borders & Edging: Plant along paths or garden beds for vibrant colour.
How to Plant Penstemon
Penstemons are easy to grow but require well-drained soil to thrive.
When and Where to Plant Penstemon
- Timing: The best time to plant penstemons is in spring after the risk of frost has passed or in early autumn while the soil is still warm.
- Location: Choose a sunny spot with at least 6 hours of direct sunlight per day. Penstemons grow best in open, well-ventilated areas.
- Soil: Free-draining, sandy, or loamy soil with a pH between 6.0 and 7.5 is ideal. Heavy clay soils should be amended with grit or organic matter to improve drainage.
Steps for Planting Penstemon
- Prepare the Soil: Mix in compost or sand to improve drainage.
- Dig a Hole: Make a hole twice as wide as the root ball.
- Plant at the Right Depth: Position the plant so the crown is just above soil level.
- Backfill and Water: Fill the hole, firm the soil gently, and water thoroughly.
- Mulch Lightly: Apply gravel or bark mulch around the base to retain moisture and suppress weeds.
Propagating Penstemon Plants
Penstemons can be propagated easily from cuttings or seeds.
Steps for Propagating Penstemon from Cuttings
- Take a Cutting: Choose a 10 cm non-flowering stem in late summer.
- Remove Lower Leaves: Strip the bottom leaves, leaving only a few at the top.
- Dip in Rooting Hormone (Optional): Speeds up root formation.
- Plant in Compost: Use a well-draining mix of perlite and compost.
- Cover and Provide Humidity: Place in a propagator or cover with a plastic bag.
- Transplant Once Rooted: After 6–8 weeks, transfer to pots or a garden bed.
Caring for Penstemon Plants
Once established, penstemons require minimal care but benefit from regular deadheading and pruning to maintain vigorous growth.
Light, Soil, and Water Requirements
- Light: Full sun encourages the best flowering and prevents leggy growth.
- Soil: Penstemons dislike heavy, wet soils and prefer dry to moderately moist conditions.
- Water: Water regularly in the first year to help establish roots. Once established, only water during prolonged dry spells.
Fertiliser Needs
Penstemons do not require heavy feeding. Over-fertilisation can lead to weak, floppy growth.
- Best Fertiliser: A balanced, low-nitrogen fertiliser applied in spring.
- Organic Options: Well-rotted compost or seaweed feed encourages healthy flowering.
Pruning and Maintenance
Regular pruning encourages bushy growth and prolongs the flowering season.
How and When to Prune Penstemons
- Deadheading: Remove faded flowers to encourage new blooms.
- Spring Pruning: In early spring, trim back old stems to about 10 cm above ground level to promote fresh growth.
- Hard Pruning (Rejuvenation Pruning): Every 3–4 years, cut back old stems to ground level to prevent woody growth.
Tip: Avoid cutting penstemons back in autumn, as old growth helps protect against winter frost.
Common Pests and Diseases
Penstemons are generally pest-resistant but can occasionally suffer from fungal diseases.
Pests
- Aphids – Can be treated with insecticidal soap or neem oil.
- Slugs and Snails – Young plants may be vulnerable; use organic slug deterrents.
Diseases
- Powdery Mildew – Affects foliage in humid conditions; improve airflow around plants.
- Root Rot – Occurs in poorly drained soil; ensure proper drainage.
Embrace the Joys of Growing Penstemon Plants
Penstemon plants are a fantastic choice for gardeners looking to add long-lasting colour, resilience, and wildlife appeal to their landscapes. Their easy-care nature, drought tolerance, and ability to thrive in a variety of conditions make them an excellent addition to any garden.
Start growing penstemons today and enjoy their vibrant, nectar-rich blooms from spring to autumn!