The illustrated growing guide
Great Blue Lobelia
Lobelia siphilitica
Family Campanulaceae
Est. zones 4-9
The blue sibling of cardinal flower and just as valuable — spikes of true blue in late summer and fall, exactly when blue is rare and pollinators need a last meal. It wants the same constantly moist soil (rain garden, pond edge) and is short-lived but self-sows to persist. Bumblebees work it hard. Pair the two lobelias for a red-and-blue moist-shade duo.
Full Sun to Part Shade
Moderate water
Moderate growth
Deer-resistant
Native to North America
Attracts hummingbirds
Attracts bees
From the print shop
Growing great blue lobelia? Hang it.
Our Wildflowers Vol. 2 collection carries great blue lobelia — Lobelia siphilitica, print Nº 13, “Blue Lobelia.”
16 designsfrom $21.99white or black groundmatte poster, unframed
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Overview
Will great blue lobelia suit your garden, and what goes wrong.
Will it thrive where you are?
Enter your ZIP — we look up your USDA hardiness zone (2023 map) and check it against what great blue lobelia actually needs.
Hardy inZones 4-9Great Blue Lobelia at a glance
Common great blue lobelia problems
- Almost none
- Rot in stagnant winter wet
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Growing
Light, water, soil, propagation and the season’s jobs.
How to grow great blue lobelia: light, water & soil
How to plant & propagate great blue lobelia
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The year
What great blue lobelia asks for, month by month.
The great blue lobelia year, month by month
BloomWhat each band means
- Bloom — flowers open — pollinators working, frost on blossoms is the danger.
The great blue lobelia year as text
- Jan quiet month
- Feb quiet month
- Mar quiet month
- Apr quiet month
- May quiet month
- Jun quiet month
- Jul quiet month
- Aug bloom
- Sep bloom
- Oct bloom
- Nov bloom
- Dec quiet month
These are the species' typical months — expect them a few weeks earlier in warm zones and later in cold ones. Watch the plant, not just the calendar.
IV
Ecology & uses
What it does for the garden, and what it is grown for.
Great Blue Lobelia in the garden system
- Herbaceous layer perennial
- Nectary/insectary
What great blue lobelia is grown for
⚠ Toxic if eatenToxic if eaten
Edibility, identification, and traditional-use notes here are general reference — not medical or veterinary advice, and not a claim that any plant treats or prevents anything. Medicinal ratings record how strongly a plant features in herbal tradition, nothing more. Never eat or dose a plant you have not positively identified. More on how to use this library.
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Cultivars
Named varieties of great blue lobelia, ruled as a catalogue.
Best great blue lobelia varieties & cultivars
Species (true blue); crosses with cardinal flower give purples ('Vedrariensis')
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Sources & plant ID
Where the care distinctions come from, and how the plant is filed.
Research basis
Sources behind this profile
No extension citations are attached to great blue lobeliayet. The care figures below come from the library's own catalogue rather than a traced primary source.
Plant ID
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Where to buy
Third-party nurseries — not Story Thyme Farms.
Third-party nurseries, not Story Thyme Farms. Prices are theirs.
Story Thyme Farms may earn a small commission from these links, at no cost to you — it never changes what we recommend.
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Questions
Great Blue Lobelia questions, answered straight.
Do deer eat great blue lobelia?
Rarely — great blue lobelia is considered deer-resistant, which makes it one of the safer unfenced choices in deer country. Hungry deer in a hard winter test every rule, but it's a low-risk pick.
Is great blue lobelia safe for kids and pets?
No — treat it as toxic if eaten. Toxic if eaten Site it accordingly if children or pets roam the garden. This is general reference, not medical or veterinary advice — call a vet or poison control if something has actually been eaten.
How do you propagate great blue lobelia?
Division or seed.
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Elsewhere
Where great blue lobelia sits in the library.
Sunflower
Zinnia
Peony
Daylily