Larkspur Delphinium vs Purple Fountain Grass Plant Comparison
Compare these two plants side by side — care needs, key differences, and which is right for your home.
Larkspur Delphinium
Delphinium spp.
Larkspurs are annual or perennial herbaceous plants known for their tall, elegant flower spikes. They typically grow to heights of 1 to 6 feet, depending on the species and cultivar. The flowers come in a wide range of colors, including blue, purple, pink, white, and yellow. Larkspurs are primarily outdoor plants, prized for their striking vertical presence in gardens and borders. They are grown for their beautiful, showy flowers that attract pollinators.
Purple Fountain Grass
Pennisetum setaceum 'Rubrum'
Purple Fountain Grass is a striking ornamental grass prized for its arching, burgundy-purple foliage and bottlebrush-like flower plumes. It typically grows in a mounded form, reaching several feet in height and width. While technically a perennial in warmer climates, it is often grown as an annual in cooler regions due to its sensitivity to frost. It is primarily an outdoor plant, grown for its dramatic texture and color in gardens and landscapes. People grow it for its ornamental value, adding movement and visual interest to borders, containers, and mass plantings.
Quick Plant Comparison
| Feature | Larkspur Delphinium | Purple Fountain Grass |
|---|---|---|
| Light | Full sun | Full sun (at least 6 hours of direct sunlight per day) |
| Watering | Every 3-7 days, depending on weather and soil drainage | Every 7-10 days, depending on weather and soil drainage |
| Humidity | 30-50% | 20-50% |
| Temperature | 15-24°C | 18-30°C |
| Care Level | Expert | Expert |
| Growth Rate | Moderate | Moderate |
| Max Height | Rarely grown indoors, outdoor height 0.3-1.8 meters | Outdoor: 0.6-1.5 meters. Indoor (unlikely to thrive): 0.3-0.6 meters |
| Pet Safety | ❌ Toxic To Pets | ✅ Safe |
| Soil | Well-draining, fertile soil with a slightly acidic to neutral pH (6.0-7.0) | Well-draining soil, such as a sandy loam or a potting mix amended with perlite |
| Beginner Friendly | ❌ No | ❌ No |
| Weekly Maintenance | 30 minutes weekly (weeding, watering, deadheading) | 15 minutes weekly |
🔬 Botanical Information — Comparing These Plants
Larkspur Delphinium
| Scientific Name | Delphinium spp. |
|---|---|
| Family | Ranunculaceae |
| Native To | Primarily Northern Hemisphere, including Europe, Asia, and North America |
| Also Known As | Larkspur, Delphinium |
| Leaves | The leaves are deeply lobed and finely divided, giving them a delicate, fern-like appearance. They are typically green or bluish-green in color and arranged alternately along the stem. |
| Flowers | Rarely flowers indoors. Outdoors, they produce tall spikes of spurred flowers in shades of blue, purple, pink, white, and yellow. The flowers bloom in summer. |
Purple Fountain Grass
| Scientific Name | Pennisetum setaceum 'Rubrum' |
|---|---|
| Family | Poaceae |
| Native To | Hybrid cultivar; species native to Africa, Southwest Asia |
| Also Known As | Purple Fountain Grass, Red Fountain Grass |
| Leaves | The leaves are long, narrow, and arching, with a deep burgundy-purple color. They have a fine texture and create a graceful, flowing appearance. |
| Flowers | It produces bottlebrush-like flower plumes that are initially a deep burgundy-purple, fading to a tan color as they mature. Flowering typically occurs in summer and fall. It is unlikely to flower indoors. |
📏 Size & Growth — Plant Comparison
Larkspur Delphinium
Purple Fountain Grass
🌱 Propagation — Comparing Plant Growth
Larkspur Delphinium
Methods: Seed, Division
Difficulty: Moderate
Tips: For seeds, cold stratification is often required. Divide established plants in early spring or fall.
Purple Fountain Grass
Methods: Seed, Division
Difficulty: Moderate
Tips: Divide clumps in spring or early summer. Sow seeds indoors 6-8 weeks before the last frost.
✨ Benefits & Features — Comparing Plant Value
Larkspur Delphinium
Larkspurs are known for their tall, elegant flower spikes and vibrant colors. They are a classic cottage garden flower and a favorite of pollinators. Their toxicity makes them unsuitable for homes with pets or small children.
- ✓ Attracts pollinators to your garden.
- ✓ Adds vertical interest and vibrant colors to outdoor spaces.
- ✓ Provides cut flowers for bouquets.
- ✓ Can be used to create a classic cottage garden aesthetic.
- ✓ Offers a sense of accomplishment for experienced gardeners.
- ⚠️ Toxic to pets
Purple Fountain Grass
Its deep purple foliage and graceful, arching habit make it a standout in any garden. The bottlebrush-like flower plumes add further visual interest and movement.
- ✓ Adds visual interest and texture to the garden
- ✓ Attracts birds
- ✓ Drought tolerant
- ✓ Deer resistant
- ✓ Provides movement in the landscape
- 🐾 Pet Safe
📅 Maintenance Schedule — Plant Care Comparison
Larkspur Delphinium
Purple Fountain Grass
🌞 Light Requirements
Larkspur Delphinium
Full sun
Low light tolerant: ❌ No
Purple Fountain Grass
Full sun (at least 6 hours of direct sunlight per day)
Low light tolerant: ❌ No
💧 Watering Needs
Larkspur Delphinium
Water deeply when the top inch of soil feels dry. Avoid overhead watering to prevent fungal diseases. Overwatering can lead to root rot, indicated by yellowing leaves and wilting. Underwatering results in dry, crispy leaves and stunted growth.
Purple Fountain Grass
Water deeply when the top inch of soil feels dry to the touch. Avoid overwatering, which can lead to root rot. Signs of underwatering include drooping or browning leaves. Signs of overwatering include yellowing leaves and soggy soil.
🌡️ Temperature & Humidity
Larkspur Delphinium
Temperature: 15-24°C
Humidity: 30-50%
Purple Fountain Grass
Temperature: 18-30°C
Humidity: 20-50%
🤔 Which Plant Is Right For You?
Larkspur Delphinium
Delphinium spp.Experienced gardeners looking to add vertical interest and vibrant colors to their outdoor flower beds.
✅ Choose This Plant If...
- You want tall, vibrant flowers in your garden.
- You want to attract pollinators to your yard.
- You have a sunny garden spot that needs a vertical accent.
- You enjoy the challenge of growing somewhat finicky plants.
- You appreciate classic cottage garden flowers.
❌ Skip This Plant If...
- You have pets or small children who might ingest the plant.
- You lack a sunny outdoor garden space.
- You are a beginner gardener looking for easy-to-grow plants.
Purple Fountain Grass
Pennisetum setaceum 'Rubrum'Gardeners looking for a dramatic ornamental grass to add color and texture to their landscape.
✅ Choose This Plant If...
- You want a striking focal point in your garden.
- You need a drought-tolerant plant for a sunny location.
- You desire a plant with beautiful purple foliage and plumes.
- You want to attract birds to your garden.
- You need a deer-resistant plant.
❌ Skip This Plant If...
- You live in a cold climate and don't want to treat it as an annual.
- You don't have a sunny location.
- You are looking for a low-maintenance indoor plant.
🎯 Quick Verdict
⚡ Key Differences Between These Plants
Larkspur Delphinium needs full sun, while Purple Fountain Grass prefers full sun (at least 6 hours of direct sunlight per day).
💡 Pro Tips For Comparing These Plants
Larkspur Delphinium Care Tips
Larkspurs are challenging to grow indoors due to their high light requirements and need for cool temperatures. They are best suited for outdoor gardens. Indoor attempts often result in weak, leggy growth and failure to flower. Proper drainage is crucial.
- Provide support for tall varieties to prevent them from falling over.
- Ensure well-draining soil to prevent root rot.
- Deadhead spent flowers regularly to encourage more blooms.
- Protect from strong winds that can damage the flower spikes.
- Monitor for pests and diseases and treat promptly.
Purple Fountain Grass Care Tips
Purple Fountain Grass is primarily an outdoor plant and will struggle indoors due to its high light requirements. It needs full sun and well-draining soil. While it can be grown in containers, it requires regular watering and fertilization. Overwintering indoors is possible in colder climates, but the plant may not thrive.
- Plant in well-draining soil in a sunny location.
- Water deeply but infrequently, allowing the soil to dry out between waterings.
- Fertilize in spring with a balanced slow-release fertilizer.
- Cut back foliage in late fall or early spring.
- Protect from frost in colder climates.
⚠️ Common Problems & Solutions — Plant Care Comparison
Larkspur Delphinium
Purple Fountain Grass
❓ Frequently Asked Questions — Comparing These Plants
Larkspur Delphinium
What are the light requirements for Larkspur Delphinium?
Larkspur Delphiniums thrive in full sun, needing a minimum of six hours of direct sunlight each day to produce abundant blooms. Insufficient light can lead to leggy growth, weak stems, and reduced flowering. When planting, choose a location that receives morning sun, which helps to dry the foliage and prevent fungal diseases.
How do I care for Larkspur Delphinium?
Larkspur Delphiniums need well-draining soil enriched with organic matter. Plant in a location with full sun, providing at least six hours of direct sunlight daily. Water deeply when the top inch of soil feels dry, but avoid overwatering. Fertilize regularly during the growing season with a balanced fertilizer, switching to a fertilizer higher in phosphorus to promote blooming.
How do I propagate Larkspur Delphinium?
Larkspur Delphiniums can be propagated by division, stem cuttings, or seed. Division is best done in spring or fall by carefully separating the root ball and replanting the divisions. For stem cuttings, take 4-6 inch cuttings from new growth in spring, remove the lower leaves, and plant in a well-draining rooting medium. Keep the cuttings moist and in a humid environment until rooted.
Purple Fountain Grass
What are the light requirements for Purple Fountain Grass?
Purple Fountain Grass requires at least 6-8 hours of direct sunlight per day to thrive and develop its characteristic vibrant purple foliage and abundant flower plumes. Insufficient sunlight can lead to leggy growth, faded color, and reduced flowering. When planting, choose a location that receives full sun throughout the day. If growing in containers, rotate the plant regularly to ensure even sun exposure on all sides. In hotter climates, some afternoon shade may be beneficial to prevent scorching, but avoid placing it in deep shade, which will hinder its growth. Supplemental lighting may be necessary if grown indoors during winter months.
How do I care for Purple Fountain Grass?
Purple Fountain Grass thrives in full sun and well-draining soil. Water thoroughly when the top inch of soil feels dry, but avoid overwatering, which can lead to root rot. Fertilize monthly during the growing season (spring and summer) with a balanced fertilizer to promote healthy growth and vibrant blooms. Prune away dead or damaged foliage in late winter or early spring before new growth emerges. In colder climates, treat it as an annual or bring it indoors during the winter. Provide adequate air circulation to prevent fungal diseases. Regularly inspect for pests like aphids or spider mites, and treat accordingly. Avoid planting in overly compacted or poorly draining soil. Mulching around the base can help retain moisture and suppress weeds. Protect from strong winds.
How do I propagate Purple Fountain Grass?
Purple Fountain Grass can be propagated by division. In early spring, carefully dig up the plant and divide the root ball into smaller clumps, ensuring each clump has healthy roots and foliage. Replant the divisions in well-draining soil and water thoroughly. Keep the soil consistently moist until the new plants are established. Division is the most reliable method. Seed propagation is possible but can be inconsistent in producing plants true to the ‘Rubrum’ cultivar. Stem cuttings are not typically used for propagating this grass. Keikis are not applicable as this plant doesn’t produce them. Ensure good air circulation to prevent fungal diseases after dividing.
Last updated: May 13, 2026 — Plant care data reviewed and verified by our editorial team.