Toxic Plant Known to be toxic - Toxic to mammals if ingested.
Image of Lobelia siphilitica
Source: Agnieszka Kwiecień
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Plant Names

image of Flowering plant
Lobelia siphilitica
Great Blue Lobelia
Lobélie bleue

Synonyms

blue cardinal flower
great lobelia

Plant Characteristics

Bloom Colour: Blue Bloom Period: Jul - Sep
Max Height: 3.0 feet
Max Width: 1.5 feet (spreads by rhizome)
Light Condition:
Full sun More than 6 hours of direct sun a day
Part shade More than 2 or 3 hours but less than 6 hours of direct sun a day
Soil conditions:
Moisture medium Tolerates medium soil condition
Lifespan: Perennial plants that will come back year after year
Gardener Experience:
beginner friendly Suitable for beginner gardeners
does not spread Does not spread uncontrollably
plant spread by rhizome Spreads by rhizome
plant germinate easy Easy to germinate
plant self seeding Self-seeding
Landscape Uses:
wetland garden Suitable for wetland garden
rain garden Suitable for rain gardens
shoreline_rehab Suitable for shoreline rehabilitation
container suitable Suitable for container garden
school garden Suitable for school gardens
boulevard garden tolerant Tolerates boulevard garden conditions
Ecological Benefits:
Hummingbird friendly Supports hummingbirds
Bird friendly Supports birds
Pollinator garden Supports pollinators
Tolerates:
Deer Resistant Deer resistant
Rabbit Resistant Rabbit resistant
Limestone Tolerant Tolerates limestone conditions
Juglone Tolerant Tolerates juglone conditions
Transplantation Tolerant Tolerates transplantation
Special Features and Considerations:

Seed and plant distribution status

No seeds available for this plant.
We currently accept seeds for this plant

Fun Facts

Great blue lobelia produces tall spikes of rich blue flowers in late summer when many other native plants have finished blooming. It thrives in moist soil and is ideal for rain gardens, pond edges, and woodland openings.

Highly attractive to bumble bees, large native bees, hummingbirds, butterflies, and hummingbird moths.

Prefers consistently moist soil.
Short-lived perennial that self-seeds gently.
Excellent companion to cardinal flower.
Cut back after frost if desired.

CAUTION
Contains lobeline and related alkaloids. Toxic if eaten in significant amounts by people or pets.

Plant Location

Native to Ottawa region: Yes

Distribution according to VASCAN

Distribution: Lobelia siphilitica
Ephemeral Native Introduced Excluded Extirpated Doubtful Absent

Thrives in Ecozones

  • Boreal Plains
  • Mixed Wood Plains

Ecological Benefits

Butterflies Supported by Lobelia siphilitica

Specialized Bees Supported by Lobelia siphilitica

No bee data available for this plant.

Complementary Plants

Substitute For Non-Native Plants

  • Buddleia (Butterfly Bush)
  • Delphinium (Delphinium)
  • Iris pseudacorus (Yellow Iris)
  • Iris (Iris Cultivars)
  • Hesperis matronalis (Dame Rocket)

Sowing Information

Download Seed Envelope Labels (PDF)
  • Sowing depth: Surface sow
  • Sow by February
  • Stratification duration: 60 days
  • Self-seeding

Harvesting and Seed Sharing

  • Harvest start month: October
  • Harvesting indicator:
    • Pods are brown, seeds are dark, and crisp, and little stem connecting the pod to the main stem is brown (not green)
  • Harvesting:
    • Cut stem (including pods), let air dry in paper bag, then shake seeds off after a few days
  • Seed viability test:
    • No test needed before donating
  • Packaging measure: Half of one, 1/32 teaspoon
  • Seed storage:
    • Air dry in paper bag or open container, for a few days until crisp
    • Shake seeds to move them once in a while to prevent molding
  • Cultivar: Yes, do not donate unless you know source, and there are no known cultivars in your garden or at proximity
  • Remove non-seed material
  • Harvesting video: Watch here

Toxicity Notes

Toxic to mammals if ingested.