Cupflower (Nierembergia scoparia)
Discover Cupflower (Nierembergia scoparia), a tender perennial offering masses of pale blue flowers from May to frost in Zones 7-10.
Complete Plant Information
Overview
The Cupflower, scientifically known as Nierembergia scoparia, provides a wonderfully dense, shrubby display perfect for adding texture and continuous color to the summer garden. This plant is prized for its abundance of delicate, cup-shaped, pale blue flowers that persist robustly from early summer until the first frost arrives. While botanically a tender perennial hardy in Zones 7 through 10, many gardeners treat Nierembergia scoparia as a reliable annual, especially in cooler northern climates. Its fine-textured foliage contrasts beautifully with the starry blooms, making it an excellent structural plant for borders, containers, and rock gardens.
Fast Facts
- Plant Family: Solanaceae
- Plant Type: Herbaceous perennial
- Native Range: Argentina, Brazil, Uruguay
- Hardiness Zones: USDA Zones 7-10
- Size at Maturity:
- Height: 1-2.5 ft
- Spread: 1-2.5 ft
- Bloom Time: May to frost
- Bloom Description: Pale blue
- Sun Exposure: Full sun to part shade
- Water Needs: Medium
- Maintenance Level: Medium
How to Grow
To successfully establish Nierembergia scoparia, plan to start seeds indoors 6 to 8 weeks before your last expected frost date, or sow directly into the garden one to two weeks prior to that date. This plant thrives in moist, organically rich, well-drained soils. Placement should capitalize on habits; aim for full sun, though providing some part afternoon shade is recommended in hotter climates where flowering may taper off. Keep soils uniformly moist, especially during initial establishment and peak summer heat.
Ongoing maintenance for Cupflower involves encouraging continuous bloom cycles. Pinching young plants early encourages a bushier, more compact habit rather than leggy growth. Remember to deadhead spent flowers to stimulate repeat blooming throughout the season. A summer mulch is highly beneficial, as it helps retain necessary soil moisture and keeps the root zone cool—which Nierembergia scoparia prefers.
If temperatures are mild, plants sited in a protected southern exposure location might survive winter in Zone 7. For guaranteed return, or if you wish to save stock, take cuttings in late summer for overwintering indoors. If summer heat causes flowering to slow significantly, a mid-season cutback will encourage a second flush of blooms later in the season.
Landscape Uses
The versatility of Cupflower makes it an invaluable component in almost any sunny garden location. Because of its compact, spreading mound habit, it excels when used as a formal edge for garden beds or along winding walkways where its low profile will not obstruct views. Its continuous flowering makes it ideal for mass planting in mixed borders, providing a solid wash of pale blue color throughout the season.
Beyond traditional borders, Nierembergia scoparia performs exceptionally well in containers. Plant it near the edge of hanging baskets or mixed container arrangements where its trailing tendency can soften hard edges. In rock gardens, it blends seamlessly with smaller, slow-growing drought-tolerant companions, offering a contrast in texture while thriving in similar well-drained conditions.
Standout Features
Flower Qualities
- Showy
Noteworthy Characteristics
Nierembergia scoparia, commonly called cupflower or tall cupflower, is a shrubby tender perennial that grows in a dense spreading mound to 12-30” tall. Cup-shaped, pale blue flowers (to 1” wide) cover the plant with bloom from early summer to fall. Finely-cut, stiff, linear to spathulate leaves to 3/4” long define the foliage structure which supports the overall shrubby mass.
Tolerances
Potential Problems
Generally, this plant exhibits few serious insect or disease issues, making it a reliable choice for low-stress gardening. However, gardeners should remain vigilant for signs of damage from slugs and snails, particularly when plants are young or environments are damp. It is also listed as susceptible to tobacco mosaic virus, so avoid planting near or using tools that have touched infected tomato or tobacco plants. Promptly removing spent foliage and ensuring good air circulation can mitigate fungal risks that sometimes accompany humid conditions.
Frequently Asked Questions
What hardiness zones is Cupflower suitable for?
Nierembergia scoparia is winter hardy in USDA Zones 7 through 10, behaving as a medium-maintenance perennial in these regions.
How large does Cupflower grow?
This plant typically forms a dense, spreading mound, reaching heights between 1 and 2.5 feet with a comparable spread of 1 to 2.5 feet.
What sun exposure does Cupflower need?
Cupflower performs best when sited where it receives full sun to light part shade. In very hot summers, afternoon shade is beneficial for maintaining consistent bloom.
When does Cupflower bloom?
You can expect Nierembergia scoparia to bloom continuously from May all the way through the first frost, displaying masses of pale blue flowers.
Conclusion
The enduring floral display and neat, mounding habit cement the value of Nierembergia scoparia in any sunny border or container grouping. This Cupflower offers a long season of easy color, provided its moisture needs are met, particularly during summer heat waves. Before planting, verify that your local conditions align with USDA Zones 7-10 or plan to treat it as a spectacular annual treat.
Companion Planting
When selecting partners for Nierembergia scoparia, focus on plants that share a similar need for medium moisture and well-drained soil, enhancing the overall visual appeal. Combine the airy texture of the Cupflower with broad-leaved companions for contrast; consider hostas (in partial shade areas) or low-growing sedums for sunnier spots. Plants with hot-colored blooms, such as orange or yellow calibrachoa or calibrachoa, create a striking complementary color palette against the cool, pale blue flowers of the Nierembergia scoparia.
Seasonal Care Calendar
Spring preparation is key to a successful summer for your Nierembergia scoparia. After all danger of frost has passed, set out purchased plants or transplants established from seed. Ensure the soil is organically rich and consistently moist at planting time. During the growing season, the primary focus is regular watering to maintain even soil moisture, avoiding deep drying out, especially during heat spells. If growth appears leggy or bloom production wanes mid-summer, apply a moderate cutback to rejuvenate the plant and encourage a fresh burst of flowering before autumn commences.
