Coral bells (Heuchera 'Obsidian')
Heuchera 'Obsidian' offers intensely dark, nearly black foliage that maintains color year-round. These low-maintenance coral bells thrive in sun to part shade.
Complete Plant Information
Overview
Heuchera ‘Obsidian’, a popular cultivar of coral bells, is prized by gardeners for its intensely dark, glossy foliage, which appears almost black throughout the growing season. This clump-forming hybrid creates a striking contrast against lighter greens and flowers, making it an exceptional specimen or accent plant. As an evergreen to semi-evergreen perennial, it offers structure and color even when little else is active.
This variety showcases dense, rounded leaves forming a basal mound, typically reaching up to 10 inches tall. Slender stems rise gracefully above the mound, displaying airy sprays of creamy white, bell-shaped flowers in early summer. Heuchera ‘Obsidian’ is valued for its relatively low maintenance demands, provided its cultural needs regarding soil and moisture are met.
Coral bells, in general, provide year-round architectural interest, and ‘Obsidian’ delivers this with maximum drama. Its presence in the garden ensures that deep, rich color is always available, whether used for year-round texture or as a vibrant contrast to flowering perennials.
Fast Facts
- Plant Family: Saxifragaceae
- Plant Type: Herbaceous perennial
- Hardiness Zones: USDA Zones 4-9
- Size at Maturity:
- Height: 1-2 ft
- Spread: 0.75-1.5 ft
- Bloom Time: June to July
- Bloom Description: Creamy white
- Sun Exposure: Full sun to part shade
- Water Needs: Medium
- Maintenance Level: Low
How to Grow
Planting Heuchera ‘Obsidian’ is best done in the spring or fall when conditions are mild, ensuring the medium moisture, well-drained soil structure is rich in organic matter. While coral bells generally prefer part shade, particularly protection from hot afternoon sun in southern regions, ‘Obsidian’ can handle full sun in northern climates provided consistent moisture is maintained. Scorch or decline can occur quickly if the soil dries out, especially in brighter locations, so plan placement carefully.
Watering should be consistent; aim for medium moisture levels without allowing the soil to become waterlogged, which can encourage root issues. Pruning involves the simple removal of faded flower stems in mid-summer to encourage any potential rebloom and maintain a tidy appearance. Foliage often remains evergreen in warmer zones, but in colder areas, a winter compost mulch applied after the ground freezes helps prevent damaging root heaving.
To maintain vigor, divide the clumps of Heuchera ‘Obsidian’ every three to four years during the spring. This division is necessary because, unlike species plants which can be grown from seed, hybrids like ‘Obsidian’ perform best when propagated horticulturally via division. Consistent care ensures the dark foliage remains vibrant throughout the season.
Landscape Uses
Heuchera ‘Obsidian’ is incredibly versatile, serving as an outstanding structural element in various garden settings. Its deep, almost black foliage makes it ideal for mass planting where they can form a dramatic, unified dark carpet. Alternatively, planting coral bells in distinct groups of three or five near the front of borders provides strong focal points.
These plants excel as edgers along pathways or walkways, where their mounding habit creates low, clean lines devoid of gaps. In rock gardens or open woodland settings, ‘Obsidian’ provides necessary year-round depth. Consider pairing Heuchera ‘Obsidian’ with plants offering bright lime green, silver, or soft pink/lavender flowers for maximum visual impact.
The dark color also allows these coral bells to anchor mixed containers beautifully, offering necessary darkness that makes surrounding, brighter annuals or perennials pop. Ensure whatever companion plant is selected shares similar cultural needs for soil drainage and water.
Standout Features
Flower Qualities
- Showy
Noteworthy Characteristics
Heuchera, commonly called coral bells or alumroot, is a genus consisting of about 55 species of evergreen to semi-evergreen herbaceous perennials which are all native to North America. ‘Obsidian’ is a specific clump-forming hybrid noted for its rounded, long-petioled leaves that emerge in a compact basal mound, maintaining their signature dark purple to almost black color. Small, creamy white flowers appear on wiry stems rising above the foliage, often reaching 20-24 inches high, providing a delicate contrast to the robust leaf color.
Tolerances
- Good resistance to powdery mildew
Potential Problems
Frost heaving of roots can be a significant issue when winter temperatures experience wide fluctuations; apply a protective winter compost mulch only after the ground has frozen solid to mitigate this risk. Cultivars of coral bells can sometimes succumb to fungal issues like powdery mildew or rust, although ‘Obsidian’ exhibits good resistance. Watch for potential insect problems, specifically weevils and foliar nematodes, though they are not typically major threats in a well-maintained garden.
Frequently Asked Questions
What hardiness zones is Coral bells suitable for?
Heuchera ‘Obsidian’ is hardy across a wide range, suitable for USDA Zones 4 through 9.
How large does Coral bells grow?
This cultivar typically reaches a height between 1 and 2 feet tall, with a spread ranging from 0.75 to 1.5 feet wide for the foliage mound and flower stalks combined.
What sun exposure does Coral bells need?
Heuchera ‘Obsidian’ performs well across a spectrum from full sun to part shade, though afternoon shade is recommended in hotter climates to prevent leaf scorch.
When does Coral bells bloom?
The bloom time for this Heuchera hybrid is typically from June through July, producing creamy white flowers.
Conclusion
Heuchera ‘Obsidian’ is a cornerstone plant for adding deep, year-round color and rich texture to the garden landscape. Its superb low maintenance level combined with its striking, almost black foliage solidifies its status as a must-have perennial. Before planting, verify that your site offers the rich, well-drained conditions required for this spectacular coral bells variety to thrive.
Propagation Tips
Since Heuchera ‘Obsidian’ is a named hybrid, propagating it successfully requires division rather than seed sowing. The optimal time to divide these clumps is in the spring, allowing the separated sections a full growing season to reestablish strong root systems before winter. Gently lift the clump with a garden fork, separating the root ball into sections, ensuring each division retains healthy roots, shoots, and at least two to three leaves.
Dividing your Heuchera ‘Obsidian’ every three to four years prevents the center of the clump from dying out and keeps the individual plants vigorous. Freshly divided coral bells should be replanted immediately into the amended soil at the same depth they were previously growing. Provide consistent water after division to reduce transplant shock and encourage rapid new growth.
Companion Planting
The dark, nearly black leaves of Heuchera ‘Obsidian’ act as a dramatic foil for almost any color, making companion selection easy. Pair it with plants that possess chartreuse or lime-green foliage, such as Hakonechloa grasses or certain Hostas, to maximize the contrast and brighten shady areas. For sunny borders, annuals like bright yellow Petunias or white Impatiens work well near these coral bells.
When planning ground cover in woodland gardens, consider using softer textures near the angular shapes of Heuchera ‘Obsidian’. Ferns provide an excellent textural backdrop, while creeping groundcovers like Lamium or Ajuga can softly spill over edges near the mound of dark leaves. Ensure companions also prefer medium moisture and well-drained soil to maintain the health of your Heuchera.
