Cardinal Flower (Lobelia cardinalis)

Cardinal Flower

Lobelia cardinalis

Vibrant scarlet spires cut through summer greenery like living torches. Herbaceous perennial; common name: Cardinal Flower.

Partial sun
1–2/week
Moderate
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Plant Needs

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Sunlight Prefers partial sun with morning direct light and afternoon shade in hot climates; tolerates full sun in cool temperate regions
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Watering Keep soil consistently moist but not waterlogged; avoid allowing the root zone to dry out completely
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Temperature Hardy to USDA zones 3–9; tolerates light frost, avoid prolonged extreme heat above 32°C
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Characteristics

  • Leaf: Lance-shaped, dark green, serrated margins, arranged alternately on erect stems
  • Flower: Tubular scarlet red blooms in dense terminal spikes; bilaterally symmetric, attractive to hummingbirds
  • Stem: Erect, smooth-textured, green to reddish, sparsely branched or unbranched
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Care Guide

Watering

Keep soil evenly moist; water deeply when the top 2 cm of soil feels dry

Fertilization

Diluted balanced liquid feed every 2 weeks. Avoid over-fertilization to prevent leggy growth; discontinue feeding in late autumn

Composted banana peel tea:Steep fully composted banana peels in water for 24 hours; dilute 1:20 for root drench; avoid raw peels to prevent pest infestations
Pruning
  • Deadhead spent flower spikes to encourage extended blooming
  • Cut back stems to ground level after the first autumn frost
  • Thin overcrowded clumps in early spring to improve airflow and reduce disease risk
  • Remove yellowing or damaged leaves throughout the growing season
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Toxicity

Warning: this plant may be toxic.

Pets & Humans

Pets: ASPCA: Toxic; contains lobeline, leading to vomiting, diarrhea, excessive salivation, and lethargy

Humans: Contains lobeline; ingestion causes mild nausea, oral irritation, or dizziness in large quantities

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Garden Uses & Culture

Culture: Symbolizes devotion and passionate love in traditional floral language

Usage: Ornamental garden plant; attracts hummingbirds, butterflies, and bees