If you are looking for a long-blooming annual plant for your patio, or one that fits in a small space, consider Nierembergia, also known as cupflower. From early summer through fall, it is covered in blue, purple, or white star-shaped saucer-like flowers with yellow centers. The airy, fine-textured foliage is attractive too.
Nierembergia grows in neat, spreading mounds so it’s a good choice for containers, hanging baskets, borders, edging, rock gardens, and along ponds. It is also a great groundcover plant that will camouflage the not-so-pretty bases of other plants in your flower beds by decoratively trailing and spilling over.
Another big plus is that deer will leave it alone.
When you shop for Nierembergia plants or seeds, be prepared for some confusing botanical nomenclature. There are several Nierembergia species and their names are often used interchangeably. The two most popular species are Nierembergia scoparia and Nierembergia hippomanica. Nierembergia scoparia is the taller, more shrub-like species, and Nierembergia hippomanica is the dwarf, more compact species. However, the names are not always properly used, so make sure to also pay attention to plant size specifications on the label.
|Botanical Name||Nierembergia scoparia, Nierembergia hippomanica, Nierembergia caerulea, Nierembergia frutescens, Nierembergia linariifolia|
|Common Name||Cup flower|
|Plant Type||Perennial grown as an annual|
|Mature Size||Nierembergia hippomanica: six to 12 inches height, 12 to 15 inches width; Nierembergia scoparia: one to two-and-a-half feet height and width|
|Sun Exposure||Full sun to part shade|
|Soil Type||Sandy, silt, loamy|
|Soil pH||6 to 8|
|Bloom Time||Mid-summer to early fall|
|Flower Color||Blue, purple, white|
|Native Area||South central Bolivia to Brazil and northern Argentina|
How to Grow Nierembergia
Nierembergia is a perennial that is grown as an annual in most areas.
Other than watering and fertilizing, the plants are low-maintenance but they benefit from deadheading spent flowers and gently trimming new growth to encourage repeated bloom.
Nierembergia can be grown in full sun but it prefers light shade during the hot afternoon hours.
The soil should be rich in organic matter and have good drainage. Mulching helps to retain soil moisture and keeps the soil cool. Using well-aged composted manure as mulch has the double benefit of keeping the soil cool and adding nutrients.
Nierembergia needs consistently moist soil so water regularly as needed. Overwatering, on the other hand, can lead to root rot and other diseases.
Temperature and Humidity
Nierembergia is heat-tolerant and highly tolerant of high humidity.
Fertilize about once a month with a complete fertilizer.
Growing in Containers
Due to its compact growth habit, Nierembergia is a good plant for containers, including hanging baskets and window boxes. Keep in mind though that container plants and hanging baskets need more frequent watering, and protect containers from the direct, hot afternoon sun to prevent root damage.
Growing From Seeds
To get a head start on summer, eight to ten weeks before your average last frost date, start seeds in flats in sterile potting soil. The seeds need light to germinate so they should be barely covered. Kept the soil evenly moist at 70 degrees F. Germination should occur within two to three weeks. Once the seedlings emerge, water less frequently and only when the soil dries out.
The seedlings will grow slowly but will take off after transplanting. After hardening off the seedlings, transplant them outdoors, six to 12 inches apart, in rich, well-drained soil. Once the plants start growing, pinch them to encourage bushy growth.
Varieties of Nierembergia
- Nierembergia hippomanica ‘Mont Blanc’ is a compact cultivar with small white flowers.
- Nierembergia hippomanica ‘White Robe’, also a compact cultivar with white flowers, blooms earlier than other varieties.
- Nierembergia scoparia ‘Purple Robe’ has blue-violet flowers.
- Nierembergia gracilis ‘Starry Eyes’, is a cultivar of a Nierembergia species that is native to the Argentinian desert and thus drought-tolerant. Its white flowers have pale lavender highlights.
- Nierembergia ‘Summer Splash’ are hybrid perennial varieties for warm climates (zone 8 to 11 depending on the variety). The compact or trailing plants have white or light blue flowers.
Nierembergia is listed as deer-resistant.