Lobelia is an annual or perennial grown for its blooms, which open from spring through fall and return year after year. It's hardy across USDA zones 10 through 11, shrugs off deer and grows just as well in a container as in the ground. Its flowers are a moderate draw for honeybees, native bees, and butterflies.
Zones
10-11
pH Range
5.5-7
Sun
Part Sun
Days to Maturity
90
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What Lobelia is
Lobelia grows as an annual or perennial and reaches around 6 inches at maturity. It blooms from spring through fall. It's also deer-resistant and well suited to containers.
How to grow Lobelia
Lobelia grows in USDA zones 10 through 11. Lobelia does best in part sun — at least 4 hours of direct sun a day — and soil from pH 5.5 to 7, on well-drained ground. It needs around 700 growing degree days to mature, which is why climate matters as much as soil.
USDA Zones
10-11
USDA PHZM 2023
Soil pH
5.5 - 7
USDA PLANTS Database
Sun
Part Sun
Growable Ground plant catalog
Drainage
well (dry spells)
Growable Ground plant catalog
Days to Maturity
90 days
Growable Ground plant catalog
GDD Required
700+
Growing degree-days of accumulated warmth it needs to mature — humid summers reach this faster than cool coastal ones.
Growable Ground plant catalog
Mature Height
0.5 ft
Growable Ground plant catalog
Frost-Free Days
0+
The frost-free stretch it needs start to finish — short-season areas may need an indoor head start.
Growable Ground plant catalog
Start the season right
Plant lobelia in part sun with at least 4 hours of direct sun. It grows in the cool halves of the year, so sow it in spring or late summer rather than waiting for midsummer heat.
Match the soil
Lobelia prefers pH 5.5 to 7 (Growable Ground Plant Database). A quick soil test from your local Extension lab tells you whether to add lime or sulfur to land in band.
Water steadily
Keep the root zone evenly moist through establishment. A 2–3 inch mulch layer holds moisture without waterlogging.
Harvest at its peak
Cut lobelia blooms in the cool of the morning, just as they open, for the longest display.
Good to know
One caution for pet owners — lobelia is toxic to dogs and cats (moderate severity). Keep it out of reach, and call ASPCA Animal Poison Control at (888) 426-4435 in an emergency. (Source: ASPCA.)
Lobelia offers moderate value to bees and other pollinators. (Source: Pollinator Partnership.)
Where Lobelia thrives
Lobelia is hardy across USDA zones 10 through 11. Zone is only the starting point, though: the soil pH, drainage, and frost dates on your specific land decide how well it actually does.
Zones 10–11·Where Lobelia growsOpen map →
On USDA hardiness-zone overlap, Lobelia can grow in these states:
See if Lobelia will thrive on your land
Zone averages are a start. Your exact soil pH, drainage, sun exposure, and frost dates shape whether lobelia actually takes — we score it against the real conditions at your address.
Three things about your exact spot that zone averages miss:
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Frequently Asked Questions
Can I grow Lobelia in my zone?
Lobelia grows in USDA hardiness zones 10 through 11 (USDA PHZM 2023). Zone is one factor — soil pH, drainage, and frost dates on your specific parcel also shape whether it takes.
When should you plant Lobelia?
Lobelia is a cool-season crop, so it goes in during the cool halves of the year — early spring, and again in late summer for a fall planting — rather than at the height of summer heat. Your local frost dates set the exact window — a Growable Ground report reads them for your address.
How much sun does Lobelia need?
Lobelia does well in partial sun — around 4 hours of direct sun, and it takes some afternoon shade in stride. That flexibility makes it a good match for a bed the house or a nearby tree shades for part of the day. A Growable Ground report maps how the sun actually falls on your land, hour by hour, so you can set it where the light lines up.
What soil does Lobelia need?
Lobelia prefers soil pH 5.5 to 7, on well-drained ground (Growable Ground Plant Database). Your report scores your parcel's actual soil against that using USDA SSURGO data.
Does Lobelia attract pollinators?
Yes — lobelia's flowers are a solid nectar source for honeybees, native bees, and butterflies. (Source: Pollinator Partnership.)
Is Lobelia safe for pets?
Lobelia is toxic to pets (dogs,cats) with moderate severity. Keep it out of reach, and call ASPCA Animal Poison Control at (888) 426-4435 in an emergency. (Source: ASPCA.)