Great Blue Lobelia
Lobelia siphilitica
Essentials
At a Glance
Plant Type
Perennial
Height
24 inches
Width
12 inches
Light
Full Sun, Partial Sun, Shade
Zones
4, 5, 6, 7, 8, 9
Water
Moderate to moist
Humidity
Prefers humid environments
Lifespan
Perennial
Native To
North America
Toxicity
Toxic if ingested; contains the alkaloid lobeline.
The Story
Plant Bio
Lobelia siphilitica is a perennial herbaceous plant known for its upright growth habit, lance-shaped green leaves, and clusters of tubular, vibrant blue flowers that attract pollinators. This species is valued for its long-lasting, striking blue flowers and its ability to thrive in moist, woodland garden settings, providing a striking vertical accent.
Bloom Period:
Uses & Benefits:
Marketplace
Where to Buy
Shipping costs Year-round shipping Free shipping
Planting
How to Grow
- Tuck seeds into moist soil in early spring.
- Keep soil consistently moist during active growth.
- Place in partial shade for best flowering.
- Mulch around base to retain moisture.
- Fertilize lightly in spring with a balanced fertilizer.
- Divide every 3-4 years in early spring or fall.
Pro Tip
Ensure soil stays moist and provide partial shade for optimal growth.
Keep It Thriving
Care Guide
Do
- Water regularly to keep soil moist 🌱
- Mulch to conserve moisture and suppress weeds
- Deadhead spent flowers to promote blooming
- Divide every few years to maintain vigor
Don't
- Allow soil to dry out completely ❌
- Expose to full, hot sun 🌞
- Over-fertilize which can reduce flowering
- Ignore pest infestations
Seasonal Care Calendar
| Task | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Deadhead | ||||||||||||
| Divide | ||||||||||||
| Spring Cleanup |
Watch Out For
Pests & Diseases
Common Pests
Common Diseases
In the Garden
Landscape Uses & Companions
Landscape Uses
Companion Plants
Multiply
Propagation Methods
Good to Know
Common Questions
Great Blue Lobelia questions
What zones can Great Blue Lobelia grow in?
Great Blue Lobelia is hardy in USDA Zones 4–9. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.
Is Great Blue Lobelia deer resistant?
Yes — Great Blue Lobelia is rated deer-resistant. Deer typically pass it over, though extreme hunger can override any plant's defenses.
When does Great Blue Lobelia bloom?
Great Blue Lobelia typically blooms in late summer through late fall. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.
Does Great Blue Lobelia need full sun?
Great Blue Lobelia does best in full sun to part shade. In hot climates, afternoon shade keeps blooms fresher longer.
More Lobelia to compare
Cardinal Flower
Lobelia cardinalis
Fan Cinnabar Rose Lobelia
Lobelia x speciosa 'Fan Cinnabar Rose'
Hybrid Cardinal Flower
Lobelia x speciosa 'Compliment Violet'
Lilac Candles Great Blue Lobelia
Lobelia siphilitica 'Lilac Candles'
Cardinal Flower Deep Rose
Lobelia cardinalis 'Deep Rose'
Cardinal Flower 'Black Truffle'
Lobelia cardinalis 'Black Truffle'
Keep exploring
Explore the genus
Collections featuring this plant
Grow Great Blue Lobelia with confidence
See it in a design of your actual yard, get zone-matched care reminders, and track it season by season in your garden journal.
