Cardinal flower (Lobelia cardinalis)
Scarlet red perennial Lobelia cardinalis, the striking Cardinal flower, thrives in wet, sunny spots, attracting hummingbirds from July to September.
Complete Plant Information
Overview
The Cardinal flower (Lobelia cardinalis) is renowned for its intensely colorful, scarlet blooms that provide a critical splash of late-season vibrancy in the summer garden. This striking herbaceous perennial establishes an upright, clump-forming habit, making it an unmistakable focal point. Lobelia cardinalis is highly valued not only for its aesthetic appeal but also for its functional role in wetter garden areas and its strong attraction to hummingbirds and butterflies.
Growing easily in rich soils, the Cardinal flower demands consistent moisture; it thrives where the ground remains medium to wet throughout the growing season. Though it is a somewhat short-lived perennial, its ease of care and spectacular vertical plumes of color compensate for any necessary replanting down the line. Gardeners should site Lobelia cardinalis where its need for moisture can be reliably met, ensuring blooms persist from mid-summer into early fall.
Native to the Americas, this plant offers reliable performance for those seeking to naturalize wet meadows or create dynamic rain gardens. The vibrant floral display of Lobelia cardinalis ensures it remains a popular choice for adding dramatic vertical interest just as many other summer flowers begin to fade.
Fast Facts
- Plant Family: Campanulaceae
- Plant Type: Herbaceous perennial
- Native Range: Americas
- Hardiness Zones: USDA Zones 3-9
- Size at Maturity:
- Height: 2-4 ft
- Spread: 1-2 ft
- Bloom Time: July to September
- Bloom Description: Scarlet red, white or rose
- Sun Exposure: Full sun to part shade
- Water Needs: Medium to wet
- Maintenance Level: Low
How to Grow
Planting the Cardinal flower is best done in spring or early fall, provided the soil conditions are suitable from the outset. Select a location that offers rich, amended soil and receives full sun to partial shade. Crucially, this plant requires constant moisture; its location should never be allowed to dry out, making ideal spots near ponds, streams, or within dedicated rain gardens.
Watering is the most critical aspect of Lobelia cardinalis care. Supplemental watering is non-negotiable during dry spells, ensuring the soil remains consistently moist to wet. Fertilizing is rarely required if the soil is rich; focus instead on maintaining soil dampness. Deadheading spent flower spikes is generally unnecessary, as the plant self-seeds readily, contributing to its naturalized appearance.
In northern climates (colder end of USDA Zones 3-5), protect the root system against freezing and heaving by applying a root mulch in late fall. This mulch also aids significantly in retaining vital soil moisture during hot summer months. While generally low maintenance, be prepared for potential nibbling damage from slugs and snails.
Landscape Uses
The natural habitat of the Cardinal flower—streamsides, swamps, and low wooded areas—informs its best landscape applications. It is exceptional when used to naturalize in wet meadows or along the edges of water features. Consider using Lobelia cardinalis as a striking vertical accent in rain gardens, where its water requirements are easily satisfied, or along pond borders.
For border plantings, group the Cardinal flower with other moisture-loving species that share similar cultural needs but offer contrasting foliage or bloom times, such as iris or cardinal flower’s cousins in the moisture-loving perennial group. Its height (up to 4 feet) helps it anchor the middle or back of a mixed border, provided its lower environment stays saturated.
The intense scarlet color demands attention; utilize this quality by planting masses of this species for maximum impact, or strategically place single specimens near viewing areas to highlight the hummingbird activity they attract.
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.
Tolerances
- Rabbit
- Deer
- Wet Soil
Potential Problems
Lobelia cardinalis exhibits excellent overall resistance to serious insect or disease issues, keeping maintenance low. However, gardeners should be vigilant against soft-bodied pests such as snails and slugs, which may readily feed upon and damage the foliage, especially when plants are young or conditions are damp.
The most vital warning involves toxicity: the foliage of Lobelia cardinalis contains alkaloids that are highly toxic to humans if ingested, so exercise caution when handling or planting near curious pets or small children. While some hybrid lobelias can struggle with unforeseen cultural issues, the straight species is generally robust when its specific wet soil needs are met.
Frequently Asked Questions
What hardiness zones is Cardinal flower suitable for?
The Cardinal flower (Lobelia cardinalis) is adaptable across USDA hardiness zones 3 through 9.
How large does Cardinal flower grow?
This perennial typically reaches a mature height between 2 and 4 feet, with a spread ranging from 1 to 2 feet wide.
What sun exposure does Lobelia cardinalis need?
Lobelia cardinalis prefers full sun to part shade; in hotter climates, supplemental afternoon shade is often beneficial to prevent drying out.
When does Cardinal flower bloom?
The spectacular floral display of the Cardinal flower occurs late in the season, blooming typically from July through September with scarlet red, white, or rose flowers.
Conclusion
The breathtaking vertical spikes of scarlet color make the Cardinal flower (Lobelia cardinalis) an irreplaceable asset to gardens demanding moisture and late-season drama. Its low maintenance requirements, coupled with undeniable wildlife appeal, confirm its status as a premier wetland perennial. Ensure consistent hydration, check your local hardiness zone compatibility, and plant this superb North American native for guaranteed summer fireworks.
Wildlife Benefits
The specific structure of the Cardinal flower attracts its most famous admirers: hummingbirds. The tubular, nectar-rich scarlet flowers are perfectly shaped for these fast-moving aerial foragers, making Lobelia cardinalis a crucial nectar source during its late-season bloom time. This strong association means planting just a few clumps can transform a section of your garden into a lively wildlife magnet.
Furthermore, the late bloom period is essential for supporting pollinators preparing for migration or winter. While the flowers are a major draw for birds, butterflies also readily visit the blooms for sustenance. Site your Lobelia cardinalis near windows or seating areas to best observe and enjoy this vibrant pollinator activity.
Companion Planting
When planning a damp border featuring Lobelia cardinalis, successful companion plants are those that share a high demand for consistent moisture. Consider pairing it with tall, stately plants like Swamp Milkweed (Asclepias incarnata) which blooms slightly earlier, or moisture-loving irises such as Blue Flag Iris (Iris versicolor).
For textural contrast against the flat, lance-shaped leaves of the Cardinal flower, incorporate bold, upright grasses adapted to wet soil, such as Switchgrass (Panicum virgatum) in its drier-tolerant cultivars, or large sedges. These groupings create a naturalistic, multi-layered effect reminiscent of a healthy waterside ecosystem.
