Bells of Ireland vs Penstemon Plant Comparison
Compare these two plants side by side — care needs, key differences, and which is right for your home.
Bells of Ireland
Moluccella laevis
Bells of Ireland is an annual flowering plant known for its tall spikes of vibrant green, bell-shaped calyces (modified leaves) that surround tiny, inconspicuous white flowers. It typically grows to a height of 2-3 feet. While it can be grown indoors, it's primarily an outdoor plant, often cultivated in gardens for its unique architectural form and long-lasting cut flowers. People grow it for its ornamental value, particularly in floral arrangements, where its bright green color adds a striking contrast.
Penstemon
Penstemon spp.
Penstemon is a diverse genus of flowering plants, primarily herbaceous perennials, known for their vibrant, tubular flowers. They range in size from a few inches to several feet tall, with varying growth habits from upright to spreading. The flowers come in a wide array of colors, including shades of blue, purple, pink, red, and white, attracting pollinators like bees and hummingbirds. Penstemons are primarily grown outdoors in gardens and naturalized areas for their showy blooms, drought tolerance, and ability to attract wildlife. They are not typically grown indoors due to their high light requirements and need for specific environmental conditions.
Quick Plant Comparison
| Feature | Bells of Ireland | Penstemon |
|---|---|---|
| Light | Full sun to partial shade outdoors. Indoors, requires very bright, direct light for at least 6 hours daily. | Full sun to partial shade. Requires at least 6 hours of direct sunlight daily for optimal flowering. |
| Watering | Outdoors: 2-3 times per week, depending on weather. Indoors: Every 5-7 days, depending on light and humidity. | Every 1-2 weeks, depending on weather and soil drainage. |
| Humidity | 40-60% | 30-50% |
| Temperature | 15-24°C | 15-27°C |
| Care Level | Expert | Expert |
| Growth Rate | Fast | Moderate |
| Max Height | Indoors: 0.6-1 meter (2-3 feet). Outdoors: 0.6-1 meter (2-3 feet) | 0.3-1.2 meters (outdoors) |
| Pet Safety | ✅ Safe | ❌ Toxic To Pets |
| Soil | Well-draining potting mix or garden soil. A mix of potting soil, perlite, and vermiculite is suitable. | Well-draining soil, such as a sandy or gravelly loam. Avoid heavy clay soils. |
| Beginner Friendly | ❌ No | ❌ No |
| Weekly Maintenance | 30 minutes weekly | 15 minutes weekly (outdoor) |
🔬 Botanical Information — Comparing These Plants
Bells of Ireland
| Scientific Name | Moluccella laevis |
|---|---|
| Family | Lamiaceae (Mint family) |
| Native To | Western Asia (Turkey, Syria, Caucasus) |
| Also Known As | Bells of Ireland, Molucca Balm, Shellflower |
| Leaves | The leaves are light green, oval to rounded in shape, and have slightly toothed edges. They are arranged oppositely along the stem and are generally inconspicuous compared to the prominent calyces. |
| Flowers | The actual flowers are small, white, and relatively insignificant, hidden within the larger green calyces. Flowering typically occurs in summer. |
Penstemon
| Scientific Name | Penstemon spp. |
|---|---|
| Family | Plantaginaceae |
| Native To | North America, particularly western North America |
| Also Known As | Beardtongue, Penstemon |
| Leaves | Leaves are typically lance-shaped to oval, arranged oppositely along the stem. They can be smooth or slightly hairy, and vary in color from green to bluish-green. Leaf size varies depending on the species. |
| Flowers | Penstemon rarely flowers indoors due to insufficient light. Outdoors, they produce showy, tubular flowers in a wide range of colors, including blue, purple, pink, red, and white. Flowers are arranged in clusters or spikes at the ends of stems. |
📏 Size & Growth — Plant Comparison
Bells of Ireland
Penstemon
🌱 Propagation — Comparing Plant Growth
Bells of Ireland
Methods: Seed
Difficulty: Moderate
Tips: Sow seeds indoors 6-8 weeks before the last frost or directly outdoors after the last frost. Seeds require light to germinate, so press them gently into the soil surface. Keep the soil consistently moist.
Penstemon
Methods: Seed, stem cuttings, division
Difficulty: Moderate
Tips: For stem cuttings, take cuttings in late spring or early summer and root them in well-draining soil. Division can be done in early spring or fall. Seeds can be sown in spring or fall.
✨ Benefits & Features — Comparing Plant Value
Bells of Ireland
The most striking feature is the bright green, bell-shaped calyces that surround the tiny white flowers. These calyces persist long after the flowers have faded, providing extended ornamental value. It is not native to Ireland, despite its common name.
- ✓ Adds unique architectural interest to gardens and floral arrangements.
- ✓ Provides a vibrant green color that contrasts well with other flowers.
- ✓ Attracts pollinators like bees and butterflies.
- ✓ Symbolizes luck and good fortune.
- ✓ Can be dried and used in dried flower arrangements.
- 🐾 Pet Safe
Penstemon
Penstemon's tubular flowers are specifically adapted for pollination by bees and hummingbirds, showcasing a co-evolutionary relationship. The sterile stamen, or beardtongue, is a distinctive feature of the genus. Many species are native to specific regions and play important roles in local ecosystems.
- ✓ Attracts pollinators, supporting local ecosystems.
- ✓ Adds vibrant color and visual interest to gardens.
- ✓ Drought-tolerant, reducing water consumption.
- ✓ Relatively deer resistant, protecting from browsing.
- ✓ Provides a source of nectar for hummingbirds and bees.
- ⚠️ Toxic to pets
📅 Maintenance Schedule — Plant Care Comparison
Bells of Ireland
Penstemon
🌞 Light Requirements
Bells of Ireland
Full sun to partial shade outdoors. Indoors, requires very bright, direct light for at least 6 hours daily.
Low light tolerant: ❌ No
Penstemon
Full sun to partial shade. Requires at least 6 hours of direct sunlight daily for optimal flowering.
Low light tolerant: ❌ No
💧 Watering Needs
Bells of Ireland
Outdoors: Water regularly, keeping the soil consistently moist but not waterlogged. Indoors: Water thoroughly when the top inch of soil feels dry. Overwatering can lead to root rot; underwatering will cause wilting and browning of the calyces.
Penstemon
Water deeply when the top inch of soil is dry. Avoid overwatering, as Penstemons are susceptible to root rot. Allow the soil to dry out slightly between waterings. Signs of overwatering include yellowing leaves and wilting, while underwatering can cause leaf drop and stunted growth.
🌡️ Temperature & Humidity
Bells of Ireland
Temperature: 15-24°C
Humidity: 40-60%
Penstemon
Temperature: 15-27°C
Humidity: 30-50%
🤔 Which Plant Is Right For You?
Bells of Ireland
Moluccella laevisExperienced gardeners who want a unique and striking addition to their cut flower arrangements.
✅ Choose This Plant If...
- You want a unique and striking addition to your garden or floral arrangements.
- You enjoy the challenge of growing plants that require specific conditions.
- You are looking for a plant with a strong architectural presence.
- You want to attract pollinators to your garden.
- You need a long-lasting cut flower with a vibrant green color.
❌ Skip This Plant If...
- You have limited sunlight indoors and cannot provide supplemental lighting.
- You are a beginner gardener looking for an easy-to-grow plant.
- You live in a very hot or humid climate, which can increase the risk of fungal diseases.
Penstemon
Penstemon spp.Gardeners looking for drought-tolerant, pollinator-attracting plants for sunny locations.
✅ Choose This Plant If...
- You want to attract hummingbirds and bees to your garden.
- You need a drought-tolerant plant for a sunny location.
- You desire a long-blooming perennial with vibrant colors.
- You want a plant that is relatively deer resistant.
- You are looking for a native plant to support local ecosystems.
❌ Skip This Plant If...
- You have pets that may ingest the plant.
- You cannot provide at least 6 hours of direct sunlight daily.
- You live in a humid climate with poorly draining soil.
🎯 Quick Verdict
⚡ Key Differences Between These Plants
Bells of Ireland has fast growth, while Penstemon grows moderate.
💡 Pro Tips For Comparing These Plants
Bells of Ireland Care Tips
Bells of Ireland are best suited for outdoor gardens. Growing them indoors is challenging due to their high light requirements. Supplemental lighting is almost always necessary. Consistent watering and well-draining soil are crucial to prevent root rot. Requires careful monitoring for pests and diseases.
- Start seeds indoors 6-8 weeks before the last frost for earlier blooms.
- Provide well-draining soil to prevent root rot.
- Water regularly, especially during hot and dry weather.
- Fertilize every 2-4 weeks during the growing season with a balanced liquid fertilizer.
- Pinch back young plants to encourage bushier growth.
Penstemon Care Tips
Penstemon is primarily an outdoor plant that requires full sun and well-draining soil. It is not well-suited for indoor growing due to its high light requirements and need for specific environmental conditions. Indoor attempts are likely to fail without supplemental lighting and careful monitoring of soil moisture.
- Plant in well-draining soil to prevent root rot.
- Provide at least 6 hours of direct sunlight daily for optimal flowering.
- Deadhead spent flowers regularly to encourage more blooms.
- Water deeply but infrequently, allowing the soil to dry out slightly between waterings.
- Apply a balanced fertilizer in early spring before new growth begins.
⚠️ Common Problems & Solutions — Plant Care Comparison
Bells of Ireland
Penstemon
❓ Frequently Asked Questions — Comparing These Plants
Bells of Ireland
What are the light requirements for Bells of Ireland?
Bells of Ireland crave sunlight. They need at least 6-8 hours of direct sunlight each day to produce vibrant green calyces and strong stems. Insufficient light can lead to leggy growth, pale coloring, and reduced blooming. When grown indoors, place them near a south-facing window where they can receive ample sunlight. If natural light is limited, supplement with grow lights. Rotate the plants regularly to ensure even light exposure on all sides. When starting seeds indoors, use grow lights to ensure healthy seedling development.
How do I care for Bells of Ireland?
Bells of Ireland require full sun, at least 6-8 hours daily, to thrive. Plant them in well-draining soil with a slightly acidic to neutral pH (6.0-7.0). Water regularly, keeping the soil consistently moist but not waterlogged, especially during hot weather. Fertilize every 2-3 weeks with a balanced liquid fertilizer during the growing season (spring and summer).
How do I propagate Bells of Ireland?
Bells of Ireland are typically propagated by seed.
Penstemon
What are the light requirements for Penstemon?
Penstemon requires at least six hours of direct sunlight per day to thrive and produce abundant blooms. A location with full sun exposure is ideal. If growing Penstemon indoors, place it near a sunny window, preferably a south-facing one. Insufficient light can result in leggy growth, reduced flowering, and pale foliage. In hot climates, some afternoon shade may be beneficial to prevent scorching. Rotate the plant regularly to ensure even light exposure on all sides. Consider using grow lights to supplement natural light during the darker months of the year, especially for indoor plants.
How do I care for Penstemon?
Penstemon thrives in well-draining soil and prefers full sun, although some varieties can tolerate partial shade. Water regularly during the first growing season to establish a strong root system, then reduce watering frequency as the plant matures. Avoid overwatering, as this can lead to root rot. Fertilize in early spring with a balanced fertilizer to promote healthy growth and abundant blooms. Deadhead spent flowers to encourage continuous blooming. Prune back in late fall or early spring to maintain shape and remove any dead or damaged growth. Provide good air circulation to prevent fungal diseases. Mulch around the base of the plant to conserve moisture and suppress weeds. Penstemon is generally hardy but may benefit from winter protection in colder climates.
How do I propagate Penstemon?
Penstemon can be propagated by division, stem cuttings, and seeds.
Last updated: April 24, 2026 — Plant care data reviewed and verified by our editorial team.