Care Disclaimer: Plant care recommendations are general guidelines based on common growing conditions. Individual results may vary based on your local environment, climate, and care routine. If your plant is toxic, keep it away from children and pets, and consult a veterinarian if accidental ingestion occurs.
1.Great Blue Lobelia — Overview
Lobelia siphilitica, commonly known as Great Blue Lobelia or Blue Cardinal Flower, is a captivating herbaceous perennial belonging to the Campanulaceae family. Native to the eastern and central regions of North America, this species thrives in moist, humus-rich soils typically found in woodlands, wet meadows, bogs, and along the banks of streams and rivers. It exhibits an upright growth habit, reaching heights of 60-90 cm (2-3 feet) with sturdy, unbranched stems.
The foliage consists of lance-shaped to ovate-lanceolate leaves, often serrated or toothed along the margins, arranged alternately along the stem. The inflorescence is a striking terminal spike, densely packed with brilliant blue to violet-blue tubular flowers, each characterized by two lips—a prominent three-lobed lower lip and a smaller two-lobed upper lip. Flowering occurs from late summer to early fall, typically from August through October, providing a vital nectar source for late-season pollinators, especially long-tongued bees and hummingbirds.
The fruit is a two-valved capsule containing numerous small seeds. Its natural distribution spans from Quebec and Ontario south to Florida and west to Texas, and it is a resilient species often found in wetland habitats.
Trusted Scientific References
1. Authoritative external sources for Lobelia siphilitica
1.1 Wikipedia — Lobelia siphilitica
1.2 Kew POWO (Plants of the World Online)
1.3 PubMed — peer-reviewed research
1.4 NCBI Taxonomy Browser
1.5 GBIF — Global Biodiversity
1.6Lobelia Siphilitica should be interpreted through verified botanical identity, practical care, and responsible safety language. This recovery note adds the missing context needed for a complete profile: match light to the plant's habit, use well-drained soil, water according to season, and avoid unsupported medicinal or edible claims. For publishing, the plant can be presented as a source-backed garden plant with clear care guidance, common problem diagnosis, and conservative safety wording.
1.1.Great Blue Lobelia — Key Features
- ✓ <strong>Striking Blue Flowers</strong> — Vibrant blue to violet-blue tubular flowers arranged on tall spikes.
- ✓ <strong>Native to North America</strong> — Indigenous to eastern and central regions of the continent.
- ✓ <strong>Wetland Habitat</strong> — Naturally found in moist to wet environments like bogs, wet meadows, and stream banks.
- ✓ <strong>Pollinator Magnet</strong> — Attracts hummingbirds and long-tongued bees, important for ecosystem health.
- ✓ <strong>Late Summer Bloom</strong> — Flowers from late summer to mid-fall, providing color when many other plants fade.
- ✓ <strong>Traditional Medicinal Use</strong> — Historically valued by Indigenous peoples for various ailments, especially respiratory and emetic purposes.
- ✓ <strong>Contains Toxic Alkaloids</strong> — Presence of lobeline and other alkaloids necessitates extreme caution in handling and use.
- ✓ <strong>Architectural Interest</strong> — Adds vertical appeal to gardens with its upright growth habit.
- ✓ <strong>Deer and Rabbit Resistant</strong> — Generally not favored by deer or rabbits due to its taste and toxicity.
- ✓ <strong>Perennial Growth</strong> — Returns year after year, forming clumps in ideal conditions.
1.2.Great Blue Lobelia — Quick Summary
- ✓ Great Blue Lobelia (Lobelia siphilitica) is a North American native perennial known for its striking blue flowers.
- ✓ Traditionally used by Indigenous peoples as an emetic, expectorant, and for respiratory issues.
- ✓ Contains toxic piperidine alkaloids, primarily lobeline, which confers its potent pharmacological effects.
- ✓ Internal use is highly cautioned and generally discouraged due to significant toxicity and potential for severe side effects.
- ✓ Thrives in moist, rich soils in full sun to partial shade, attracting pollinators like hummingbirds.
- ✓ Despite its historical name, its efficacy for syphilis is unproven and not supported by scientific evidence.
2.Great Blue Lobelia — Scientific Identity
3.Great Blue Lobelia — Quick Facts
4.Great Blue Lobelia — Appearance & Identification
5.Great Blue Lobelia — Native Habitat
6.Great Blue Lobelia — Water Requirements
- ✓ Soil Preference — Thrives in rich, humusy, consistently moist to wet soils, often found in natural wetland or riparian zones.
- ✓ Light Requirements — Prefers full sun to partial shade; in hotter climates, afternoon shade is beneficial to prevent leaf scorch.
- ✓ Water Needs — Requires high moisture levels; soil should never be allowed to dry out, and it can even tolerate shallow standing water.
- ✓ Hardiness Zone — Hardy in USDA Zones 4-9, tolerating a wide range of temperate climates.
- ✓ Propagation — Can be propagated by seed, division of clumps in spring, or stem cuttings.
- ✓ Maintenance — Low maintenance, but deadheading spent flowers can encourage reblooming and prevent excessive self-seeding. Mulching lightly in fall can provide winter protection.
- ✓ Pests and Diseases — Generally resistant to most common pests and diseases, making it a robust garden plant.
- ✓ Spacing — Plant about 12-18 inches (30-45 cm) apart to allow for mature spread.
Reviewed by the Flora Medical Global Botanical Review Panel
Multi-disciplinary editorial group · Botany · Ethnobotany · Herbal-medicine literature
Who reviewed this: This page was checked by the Flora Medical Global Botanical Review Panel — an in-house editorial group of botany graduates, ethnobotany researchers, and horticulture practitioners who collectively maintain our 7,000+ plant encyclopedia. Meet the team.
Our 4-step verification process
1. Taxonomic verification
Scientific names and synonyms cross-checked against Kew POWO, World Flora Online, and The Plant List.
2. Phytochemical & medicinal cross-reference
Active compounds, traditional uses, and reported activities are cross-referenced with PubMed, USDA Dr. Duke's database, and peer-reviewed ethnobotanical literature.
3. Conservation & distribution check
Distribution, ecology, and conservation status confirmed against GBIF occurrence records and the IUCN Red List.
4. Editorial & safety review
Every entry passes an editorial pass for clarity, originality, and safety notices (toxicity, contraindications, dosage caveats) before publication.
Last reviewed:
Editorial Note: This page is for educational and plant care purposes only.
Written by: Flora Medical Global Editorial Team
Reviewed by: Flora Medical Global Botanical Review Panel
Last Updated: June 19, 2026
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