Cardinal flower (Lobelia cardinalis 'Black Truffle')
Lobelia cardinalis 'Black Truffle' offers stunning deep red blooms and unique dark foliage, ideal for wet areas in USDA Zones 3-8.
Complete Plant Information
Overview
Lobelia cardinalis ‘Black Truffle’ is a dramatic, dark-leaved cultivar of the native Cardinal flower, providing exceptional late-season color. This herbaceous perennial distinguishes itself immediately with emerging foliage that shines nearly black in spring before maturing to a rich maroon. Its vibrant, deep red, tubular flowers reliably appear from mid-summer into the fall, creating powerful focal points in the landscape.
Valued for both its striking aesthetics and its ecological contribution, this Lobelia cardinalis selection thrives where many other perennials struggle—in consistently moist to wet soils. It offers a stunning vertical accent, reaching heights up to four feet, while actively drawing hummingbirds and butterflies to the garden during the late summer lull.
Gardeners seeking high impact with low demands will appreciate the low maintenance nature of Lobelia cardinalis ‘Black Truffle’, provided its moisture requirements are met. Successful cultivation hinges on replicating its native streamside habitat, ensuring the soil never fully dries out during the growing season.
Fast Facts
- Plant Family: Campanulaceae
- Plant Type: Herbaceous perennial
- Hardiness Zones: USDA Zones 3-8
- Size at Maturity:
- Height: 3-4 ft
- Spread: 2-3 ft
- Bloom Time: July to September
- Bloom Description: Deep red
- Sun Exposure: Full sun to part shade
- Water Needs: Medium to wet
- Maintenance Level: Low
How to Grow
Planting Lobelia cardinalis ‘Black Truffle’ should occur when the danger of frost has passed, ideally in rich, well-amended soil. Because this Cardinal flower demands constant moisture, select the lowest spot in the garden or an area adjacent to a pond or stream. It performs well in full sun only when grown in cooler northern climates; elsewhere, ensure it receives afternoon shade protection to prevent wilting and stress.
Consistent watering is paramount for success with this cultivar. The soil should never be allowed to dry out, and the plant tolerates brief periods of flooding typical of a rain garden setting. Fertilization is rarely necessary if the native soil structure is rich, but focus your efforts on moisture retention.
As temperatures drop in cold winter climates, apply a layer of root mulch around the base of the plant. This insulating layer is vital to protect the root system from hard freezes and to mitigate root heaving caused by freeze-thaw cycles. This simple winterizing step significantly improves the longevity of this somewhat short-lived perennial.
Landscape Uses
The vibrant color and moisture needs of Lobelia cardinalis ‘Black Truffle’ make it an essential component in specialized garden designs. It is unparalleled for rain gardens, wet meadows, and edges of water features like ponds or streams where consistent saturation is guaranteed. The height provided by the flowering spikes, reaching up to four feet, adds essential vertical interest in these moist pockets.
When integrating this plant into a border, utilize it toward the back, ensuring other nearby plants share its preference for damp conditions. It pairs beautifully with moisture-loving companions such as astilbes, irises, and sedges, creating a lush, layered tapestry of texture and color. The dark foliage of the ‘Black Truffle’ variety provides striking contrast against bright greens and cool blues, enhancing the visual punch of the deep red flowers.
Standout Features
Flower Qualities
- Showy
Noteworthy Characteristics
Lobelia cardinalis, commonly called cardinal flower is a Missouri native perennial which typically grows in moist locations along streams, sloughs, springs, swamps and in low wooded areas. A somewhat short-lived, clump-forming perennial which features erect, terminal spikes (racemes) of large, cardinal red flowers on unbranched, alternate-leafed stalks rising typically to a height of 2-3’ (infrequently to 4’). Tubular flowers are 2-lipped, with the three lobes of the lower lip appearing more prominent than the two lobes of the upper lip. Finely-toothed, lance-shaped, dark green leaves (to 4” long). Late summer bloom period. Flowers are very attractive to butterflies and hummingbirds, but not cardinals. White and rose colored forms are also known.Genus name honors Matthias de l’Obel (1538-1616), French physician and botanist, who with Pierre Pena wrote Stirpium Adversaria Nova (1570) which detailed a new plant classification system based upon leaves.Specific epithet means scarlet or cardinal red.Common name is in reference to the red robes worn by Roman Catholic cardinals. ‘Black Truffle’ is a dark-leaved selection of cardinal flower. Mature clumps will reach 3-4’ tall with a 2-3’ spread. The emerging spring foliage is shiny with a nearly black coloration. With the onset of warmer summer weather, the foliage turns maroon and retains this coloration for the rest of the growing season. The 2’ tall flowering spikes bear deep red, tubular flowers from mid summer into fall. This plant is protected by patent number PP25687.
Tolerances
- Rabbit
- Deer
- Wet Soil
Potential Problems
This selection of Cardinal flower generally presents few serious challenges related to pests or diseases. The primary manageable issue involves occasional damage from snails and slugs, which may chew on the foliage, particularly when plants are young or stressed. Monitor low growth areas and employ appropriate organic controls if necessary.
It is critical to note that the foliage of Lobelia species contains alkaloids, making this plant highly toxic to humans and pets if ingested. Always plant Lobelia cardinalis ‘Black Truffle’ in areas inaccessible to curious children or grazing animals, and handle the foliage with care when pruning.
Frequently Asked Questions
What hardiness zones is Cardinal flower (Lobelia cardinalis ‘Black Truffle’) suitable for?
Lobelia cardinalis ‘Black Truffle’ is suitable for USDA Hardiness Zones 3 through 8, making it reliably perennial across a wide range of climates.
How large does Cardinal flower grow?
At maturity, this specific cultivar typically reaches a height between 3 and 4 feet, with a spread generally ranging from 2 to 3 feet wide.
What sun exposure does Cardinal flower need?
This plant prefers full sun to part shade; however, in hotter regions, afternoon shade is highly recommended to help maintain soil moisture levels.
When does Cardinal flower bloom?
The striking deep red blooms of this plant appear reliably from July through September, providing color late into the growing season.
Conclusion
The unique, nearly black foliage paired with brilliant scarlet flowers makes Lobelia cardinalis ‘Black Truffle’ an invaluable asset for damp garden spaces. Its ability to thrive in wet soil and attract vital pollinators ensures both aesthetic appeal and ecological function. Before planting, confirm your location falls within USDA Zones 3-8 and commit to maintaining consistently moist soil conditions for the very best performance from your Cardinal flower.
Wildlife Benefits
The tubular, cardinal red flowers of Lobelia cardinalis ‘Black Truffle’ are perfectly adapted for pollination by specialized visitors. These vibrant blooms are magnets for hummingbirds, offering a crucial late-season nectar source when other flowers are fading. Butterflies are also frequent visitors, utilizing the flowers for refueling during their cycles.
Attracting these high-energy pollinators requires matching the plant’s cultural needs. By placing this Cardinal flower in its preferred moist habitat, you ensure the plant remains healthy enough to produce the rich nectar flow that supports local wildlife populations throughout late summer and early autumn.
Companion Planting
Since Lobelia cardinalis ‘Black Truffle’ demands consistently wet feet, selecting companions with similar moisture requirements is key to creating a cohesive, thriving planting scheme. Excellent partners include marsh marigolds (Caltha palustris) for spring color, or moisture-loving ferns like the Ostrich fern (Matteuccia struthiopteris) for texture.
For complementary color that blooms simultaneously in late summer, consider pairing the deep red spikes with the blues and purples of hardy bog orchids or taller spikes of blue-flowering monkshood (Aconitum), provided the foliage of the Monkshood is kept away from children due to toxicity. These companions help mask the potentially short-lived nature of the blooming clump by offering varied structure across the season.
