Great Blue Lobelia Plant Care
Lobelia siphilitica L.
Updated · Sources · How we source care data
Lobelia siphilitica, the great blue lobelia, great lobelia, or blue cardinal flower, is a plant species within the family Campanulaceae. It is an herbaceous perennial dicot native to eastern and central Canada and United States.
Every 3–7 days
Full sun to part shade
50–75°F
40–70%
At a glance
How do you care for Great Blue Lobelia?
Water Great Blue Lobelia every 3–7 days, letting the top layer of soil dry out between waterings, and give it full sun to part shade. It prefers temperatures of 50–75°F (10–24°C) and 40–70% humidity. Fertilize it every 6 months during the growing season.
Where Is the Great Blue Lobelia Native To?
What Is the Great Blue Lobelia?
Great Blue Lobelia (Lobelia siphilitica) belongs to the Campanulaceae family within the Lobelia genus. Great Blue Lobelia is native to eastern and central Canada and United States. Great Blue Lobelia is also known as Blue Cardinal Flower, Cardinal Flower, Blue Lobelia.
Great Blue Lobelia displays a spreading, low-growing perennial growth habit, reaching up to 0.5 ft tall with a spread of approximately 1.5 ft. Great Blue Lobelia produces tubular flowers in shades of blue, purple, pink, or white.
Leaf size: approximately 2 inches.
How Often Should You Water a Great Blue Lobelia?
Lobelia siphilitica requires watering every 3–7 days. Allow the top layer of soil to dry between waterings to prevent root rot. Reduce watering frequency during winter when growth slows.
Watering Frequency
Every 3–7 days
Let soil partially dry between waterings
What Light Does the Great Blue Lobelia Need?
Great Blue Lobelia thrives in full sun to part shade.
Light Requirement
Full sun to part shade
What Temperature and Humidity Does the Great Blue Lobelia Prefer?
Lobelia siphilitica grows best at temperatures of 50–75°F. Great Blue Lobelia prefers humidity levels of 40–70%.
Temperature
50–75°F
Humidity
40–70%
What Soil Mix Works Best for a Great Blue Lobelia?
Moist, well-draining soil rich in organic matter. Good drainage is essential for Great Blue Lobelia to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Great Blue Lobelia?
Feed Great Blue Lobelia every 6 months during the growing season (spring and summer) with a balanced fertilizer diluted to the strength on the label.
Pause feeding in autumn and winter, when growth slows, and never fertilize dry soil — water first.
Fertilizing
Every 6 months
During the growing season
The PlantoScan app can remind you when to water and when to fertilize each plant.
How Do You Repot a Great Blue Lobelia?
Repot every 1-2 years in spring. Choose a pot one size larger than the current container, and ensure it has drainage holes to allow excess water to escape.
How Do You Propagate a Great Blue Lobelia?
Great Blue Lobelia can be propagated through seeds, division. Similar propagation techniques also apply to cardinal flower plant care, which shares the same genus.
Is the Great Blue Lobelia Toxic to Pets and Children?
Pet safety not verified
The ASPCA does not list Great Blue Lobelia, so we can't confirm whether it is safe for cats and dogs. Keep pets from chewing it as a precaution.
This is a general caution, not veterinary or medical advice. If your pet ate a plant, contact your vet or animal poison control.
See all plants toxic to cats and plants toxic to dogs.
What Pests and Diseases Affect the Great Blue Lobelia?
Great Blue Lobelia is susceptible to aphids, slugs, snails. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.
Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.
What USDA Hardiness Zone Does the Great Blue Lobelia Need?
Great Blue Lobelia grows outdoors in USDA Zone 12a. It survives winters down to planting zone 12a. Great Blue Lobelia is native to eastern and central Canada and United States. In cooler regions, grow Great Blue Lobelia as a houseplant or bring it indoors before the first frost.
Hardiness Zone
Zone 12a
Keep exploring plants
Great Blue Lobelia is one of many species covered in the complete plant care and identification guide, which groups plants by genus, attribute, and popularity.
It belongs to the Lobelia genus — compare its care with other Lobelia species on PlantoScan.
Lobelia is part of the Campanulaceae plant family — browse all Campanulaceae genera and species.
Great Blue Lobelia thrives in bright light and direct sun — see other bright-light plants.
More Lobelia Species
Other Lobelia species in PlantoScan's care catalogue share similar watering, light, and soil preferences:
Sources
- Scientific name & taxonomy: Lobelia siphilitica L., family Campanulaceae (first published in Sp. Pl. 2: 931. 1753 [1 May 1753]) — World Flora Online record, IPNI name record.
- Pet toxicity: Pet safety not verified: the ASPCA does not list Great Blue Lobelia, so we can't confirm whether it is safe for cats and dogs. Checked against the ASPCA plant list; any other toxicity note on this page comes from PlantoScan's plant database.
- Hardiness zone: USDA Zone 12a, calculated from the plant's minimum temperature.
- Care values(watering, light, temperature, humidity, soil, fertilizing): PlantoScan's plant database, filtered by automatic plausibility checks — values that fail them are hidden. How we source and check plant data.
Spotted a mistake? Email info@upvision.media with the page link — we check and correct reported errors.
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