Cup Flower vs Fountain Grass Plant Comparison
Compare these two plants side by side — care needs, key differences, and which is right for your home.
Cup Flower
Cobaea scandens
Cobaea scandens, commonly known as Cup Flower or Cup-and-Saucer Vine, is a vigorous, fast-growing perennial vine often grown as an annual in temperate climates. It is characterized by its climbing habit, using tendrils to attach to supports. The plant produces unique, bell-shaped flowers that start green and mature to a deep purple or white, resembling cups sitting on saucers. It is primarily an outdoor plant, valued for its rapid growth and ability to cover fences, trellises, and walls quickly. While occasionally grown indoors, it requires significant space and light to thrive.
Fountain Grass
Pennisetum setaceum
Fountain Grass is a perennial grass known for its graceful, arching foliage and bottlebrush-like flower plumes. Typically grown as an ornamental grass, it adds texture and movement to landscapes. It forms dense clumps of slender, linear leaves that can range in color from green to reddish-purple, depending on the cultivar. The feathery flower plumes emerge in summer and persist into fall, adding visual interest. While primarily an outdoor plant, it is sometimes grown in containers. It is valued for its drought tolerance and low maintenance requirements in suitable climates.
Quick Plant Comparison
| Feature | Cup Flower | Fountain Grass |
|---|---|---|
| Light | Full sun to partial shade outdoors. Indoors, requires very bright, direct light for several hours daily. | Full sun (at least 6-8 hours of direct sunlight daily) |
| Watering | Outdoors: Every 2-3 days in hot weather, less frequently in cooler weather. Indoors: Every 7-10 days, depending on light and humidity. | Every 1-2 weeks, depending on weather and soil drainage |
| Humidity | 40-60% | 30-50% |
| Temperature | 18-27°C | 18-30°C |
| Care Level | Expert | Expert |
| Growth Rate | Fast | Fast |
| Max Height | Outdoors: 6-12 meters. Indoors: 1-3 meters (highly dependent on support and pruning). | 0.6-1.5 meters (outdoor); significantly smaller in containers indoors (if attempted) |
| Pet Safety | ✅ Safe | ✅ Safe |
| Soil | Well-draining, fertile soil. A mix of potting soil, perlite, and compost is suitable. | Well-draining soil, such as a sandy loam or a general-purpose potting mix amended with perlite. |
| Beginner Friendly | ❌ No | ❌ No |
| Weekly Maintenance | 30 minutes weekly (pruning, watering, fertilizing). | 15 minutes monthly |
🔬 Botanical Information — Comparing These Plants
Cup Flower
| Scientific Name | Cobaea scandens |
|---|---|
| Family | Polemoniaceae |
| Native To | Mexico, Central America |
| Also Known As | Cup-and-Saucer Vine, Cathedral Bells, Mexican Ivy, Monastery Bells |
| Leaves | The leaves are pinnately compound, with 4-6 leaflets and a terminal tendril. The leaflets are ovate to elliptic, with a smooth margin and a dark green color. They are typically 5-10 cm long. |
| Flowers | It can flower indoors with sufficient light, but flowering is more prolific outdoors. The flowers are bell-shaped, about 5-7 cm in diameter, and start green before turning purple or white. They have a distinctive cup-and-saucer shape. |
Fountain Grass
| Scientific Name | Pennisetum setaceum |
|---|---|
| Family | Poaceae |
| Native To | Native to tropical Africa, Southwest Asia, and the Arabian Peninsula; naturalized in many other regions. |
| Also Known As | Fountain Grass, Crimson Fountain Grass, Purple Fountain Grass |
| Leaves | Slender, linear leaves that can range in color from green to reddish-purple, depending on the cultivar. The leaves are typically 30-90 cm long and 0.5-1 cm wide. |
| Flowers | Flowers are produced in bottlebrush-like plumes that can be pink, purple, or white. The plumes emerge in summer and persist into fall. It is very unlikely to flower indoors. |
📏 Size & Growth — Plant Comparison
Cup Flower
Fountain Grass
🌱 Propagation — Comparing Plant Growth
Cup Flower
Methods: Seed, Stem cuttings
Difficulty: Moderate
Tips: For seeds, scarify the seed coat before sowing to improve germination. For stem cuttings, take semi-hardwood cuttings in late summer and root them in a well-draining medium.
Fountain Grass
Methods: Seed, Division
Difficulty: Easy
Tips: Divide established clumps in spring or fall. Sow seeds in spring after the last frost. Ensure good drainage and consistent moisture during germination.
✨ Benefits & Features — Comparing Plant Value
Cup Flower
The cup-shaped flowers are its most distinctive feature, with their unique shape and color-changing properties. Its rapid growth rate allows it to quickly cover large areas, making it a popular choice for creating privacy screens or adding vertical interest to gardens.
- ✓ Provides quick coverage for fences and walls
- ✓ Attracts pollinators like bees and hummingbirds
- ✓ Adds a unique and exotic touch to the garden
- ✓ Offers a visually appealing display with its cup-shaped flowers
- ✓ Can be grown in containers, allowing for flexibility in placement
- 🐾 Pet Safe
Fountain Grass
Fountain Grass is known for its graceful, arching foliage and bottlebrush-like flower plumes. The flower plumes add visual interest and movement to landscapes. Its drought tolerance makes it a popular choice for xeriscaping.
- ✓ Adds visual interest to landscapes
- ✓ Provides habitat for birds and beneficial insects
- ✓ Drought-tolerant and low-maintenance
- ✓ Erosion control on slopes
- ✓ Can be used in cut flower arrangements
- 🐾 Pet Safe
📅 Maintenance Schedule — Plant Care Comparison
Cup Flower
Fountain Grass
🌞 Light Requirements
Cup Flower
Full sun to partial shade outdoors. Indoors, requires very bright, direct light for several hours daily.
Low light tolerant: ❌ No
Fountain Grass
Full sun (at least 6-8 hours of direct sunlight daily)
Low light tolerant: ❌ No
💧 Watering Needs
Cup Flower
Water deeply when the top inch of soil feels dry. Avoid overwatering, which can lead to root rot. Ensure good drainage. Indoors, allow the soil to dry out slightly between waterings. Signs of underwatering include wilting leaves; overwatering includes yellowing leaves and soggy soil.
Fountain Grass
Water deeply when the top inch of soil feels dry. Avoid overwatering, which can lead to root rot. Allow the soil to dry out slightly between waterings. Signs of underwatering include drooping or browning leaves. Overwatering can cause yellowing leaves and a mushy base.
🌡️ Temperature & Humidity
Cup Flower
Temperature: 18-27°C
Humidity: 40-60%
Fountain Grass
Temperature: 18-30°C
Humidity: 30-50%
🤔 Which Plant Is Right For You?
Cup Flower
Cobaea scandensGardeners with ample outdoor space looking for a fast-growing vine to cover structures.
✅ Choose This Plant If...
- You want a fast-growing vine to quickly cover a fence or trellis.
- You are looking for a plant with unique and interesting flowers.
- You want to attract pollinators to your garden.
- You have a sunny outdoor space where the vine can thrive.
- You enjoy a challenge and are willing to provide the specific care needed for indoor growth.
❌ Skip This Plant If...
- You have limited indoor space and cannot provide ample light.
- You are looking for a low-maintenance indoor plant.
- You live in a climate with harsh winters and don't want to overwinter the plant indoors.
Fountain Grass
Pennisetum setaceumGardeners looking for a low-maintenance, ornamental grass to add texture and movement to their outdoor landscapes.
✅ Choose This Plant If...
- You want a drought-tolerant ornamental grass for your garden.
- You appreciate the graceful, arching foliage and feathery flower plumes.
- You are looking for a low-maintenance plant that adds texture and movement to your landscape.
- You live in a warm climate where it can thrive outdoors.
- You want to attract birds to your garden.
❌ Skip This Plant If...
- You live in a region where it is considered an invasive species.
- You do not have a sunny outdoor space.
- You are looking for a plant that thrives indoors.
🎯 Quick Verdict
⚡ Key Differences Between These Plants
Both plants have similar basic care requirements but differ in appearance and specific needs. Compare plants carefully to find the best fit for your space.
💡 Pro Tips For Comparing These Plants
Cup Flower Care Tips
Cobaea scandens is primarily an outdoor plant. Growing it indoors is challenging due to its high light requirements and vigorous growth. It needs ample space, strong support, and regular pruning to manage its size. Providing adequate light is crucial for flowering indoors.
- Provide a strong support structure for the vine to climb.
- Water deeply but infrequently, allowing the soil to dry slightly between waterings.
- Fertilize regularly during the growing season to promote vigorous growth and flowering.
- Prune regularly to control size and shape, especially indoors.
- Monitor for pests and diseases and treat promptly.
Fountain Grass Care Tips
Fountain Grass is primarily an outdoor plant that thrives in full sun and well-draining soil. Growing it indoors is challenging due to its high light requirements and potential size. It requires careful watering and fertilization. It can become invasive in some regions due to its prolific seed production.
- Plant in well-draining soil to prevent root rot.
- Provide full sun for optimal growth and flowering.
- Water deeply but infrequently, allowing the soil to dry out slightly between waterings.
- Cut back foliage in late winter or early spring to encourage new growth.
- Deadhead spent flower plumes to prevent unwanted seed dispersal.
⚠️ Common Problems & Solutions — Plant Care Comparison
Cup Flower
Fountain Grass
❓ Frequently Asked Questions — Comparing These Plants
Cup Flower
What are the light requirements for Cup Flower?
Cup Flower requires bright, indirect light to thrive and produce abundant blooms. A location near an east- or west-facing window is ideal, providing several hours of gentle morning or afternoon sun. Avoid placing the plant in direct, intense sunlight, which can scorch the leaves. If growing indoors, supplement natural light with a grow light if necessary, especially during the winter months. Insufficient light can result in leggy growth, fewer blooms, and pale foliage. Rotate the plant regularly to ensure even light exposure on all sides. When growing outdoors, choose a spot that receives full sun for at least 6 hours a day, but with some protection from the harshest midday rays, especially in hotter climates.
How do I care for Cup Flower?
Cup Flower thrives with consistent care. Provide bright, indirect light, avoiding harsh direct sunlight. Water thoroughly when the top inch of soil feels dry, ensuring good drainage to prevent root rot. Fertilize regularly during the growing season (spring and summer) with a balanced liquid fertilizer diluted to half strength, focusing on formulas higher in phosphorus to promote blooming. Maintain moderate humidity levels, especially indoors, by misting or using a humidifier. Prune spent flowers to encourage continuous blooming. Repot in spring every 1-2 years into a slightly larger pot with well-draining potting mix. Monitor for pests like aphids and spider mites, treating promptly with insecticidal soap or neem oil. Provide temperatures between 60-75°F (15-24°C) for optimal growth. Reduce watering and fertilization in the fall and winter as growth slows. Ensure good air circulation to prevent fungal diseases.
How do I propagate Cup Flower?
Cup Flower can be propagated through stem cuttings, division, and, less commonly, from keiki (small plantlets that grow on the parent plant). For stem cuttings, take 4-6 inch cuttings from healthy stems, remove the lower leaves, and dip the cut end in rooting hormone. Plant the cuttings in moist potting mix and cover with a plastic bag to maintain humidity. Keep in a warm, bright location until roots develop (usually 4-6 weeks). For division, carefully separate the root ball of a mature plant into smaller sections, ensuring each section has healthy roots and stems. Replant the divisions in separate pots. Keiki propagation is rare, but if keiki develop, allow them to grow until they have roots, then carefully remove them and plant in their own pots.
Fountain Grass
What are the light requirements for Fountain Grass?
Fountain Grass requires a minimum of six hours of direct sunlight each day to thrive and produce abundant blooms. Insufficient light can lead to weak growth, fewer flowers, and a generally unhealthy appearance. When planting Fountain Grass, choose a location that receives full sun exposure throughout the day.
How do I care for Fountain Grass?
Fountain Grass thrives in full sun and well-drained soil. Water deeply but infrequently, allowing the soil to dry out slightly between waterings. Fertilize in spring with a balanced fertilizer to promote healthy growth and abundant blooms. Prune back dead foliage in late winter or early spring before new growth emerges.
How do I propagate Fountain Grass?
Fountain Grass is easily propagated by division. In early spring, carefully dig up the clump and divide it into smaller sections, ensuring each section has healthy roots and foliage. Replant the divisions in well-drained soil and water thoroughly. Stem cuttings are not a reliable method. Keikis do not naturally occur on Fountain Grass.
Last updated: May 5, 2026 — Plant care data reviewed and verified by our editorial team.