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Lobelia
Lobelia erinus
Lobelia blooms from May through September.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Lobelia
Plant it in part sun. It prefers moderate water. Expect it to reach about 8 in tall and 10 in wide at maturity, in roughly 1 year (not yet checked).
What was checked
Mature height and spread, hardiness zones, sun and the trait tags were checked against named botanical sources for this plant. The bloom months and water need on this page were not, and each fact above says which. The planting, spacing and size sections are derived from these checked facts by a fixed rule, not checked separately, and the plant type is the library's own classification.
When to plant Lobelia
Wait until all danger of frost has passed, then plant out Lobelia into warm soil; in most zones that means late spring. Planted then, it flowers from May to September.
Month-by-month timing for your zone is on the planting calendar. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Lobelia get?
8 intall5 ft 7 inan adult10 inwideSee Lobelia in a garden plan: the planner shows it in 3D beside everything else you add, growing toward this size over the years.
How far apart to plant Lobelia
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Lobelia about 10 in apart, center to center, so each plant has room to reach its full width.
Add Lobelia to a garden plan and the planner draws it at its full width, so you see the spacing before you buy.
Where these facts come from
Lobelia's height, spread, hardiness zones, sun and trait tags were checked against 7 published sources on July 30, 2026. Each one is linked below with every fact it carried, which can include a fact this page still marks as not yet checked, because a source carrying a value is not the same as the value being held to the standard. Facts not in that list, and the planting, spacing and size sections, are not covered by these sources.
- Missouri Botanical GardenLobelia erinusheight, spread, hardiness zones, sun and trait tags
- NC State ExtensionLobelia erinusheight, spread, hardiness zones, sun and trait tags
- edis.ifas.ufl.eduUniversity of Florida IFAS Extension, EDIS FPS-351 (Lobelia erinus, ed...height, spread, sun and trait tags
- University of Arkansas Extensionedging lobelia, Lobelia erinusheight, spread, sun and trait tags
- asu.eduArizona State University plant files, Chris Martin (Lobelia erinus)height, spread and sun
- Proven Winnersannual lobelia, Lobelia erinushardiness zones, sun and trait tags
- RHSRoyal Horticultural Society (Lobelia erinus, trailing lobelia)height, spread and sun
How the checking works, and what each standard covers, is on the verified plants page.
Comes in 5 varieties across 4 colors
Same plant, same care - pick the color you are growing.
Compare every variety in the Lobelia group
Every figure is the variety's own page fact. Tap a name to open it.
| Variety | Color | Blooms | Hardiness | Sun | Size (H × W) |
|---|---|---|---|---|---|
| Crystal Palace | Blue | May–Sep | Annual (replant yearly) | Part sun | 6 in × 8 in |
| Lilac | Purple | May–Sep | Annual (replant yearly) | Part sun | 8 in × 10 in |
| Lobeliathis page | Blue | May–Sep | Annual (replant yearly) | Part sun | 8 in × 10 in |
| Rose | Pink | May–Sep | Annual (replant yearly) | Part sun | 8 in × 10 in |
| Sky Blue | Blue | May–Sep | Annual (replant yearly) | Part sun | 8 in × 10 in |
| White | White | May–Sep | Annual (replant yearly) | Part sun | 8 in × 10 in |
Good to know about Lobelia
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note. A note reports what its source says; where that differs from a fact above, the fact above is this entry's stored value, and its mark says whether it has been checked.
Safety
Toxic to dogs, cats and horses, and to people if eaten in quantity. All parts hold lobeline, a nicotine-like alkaloid; keep pets and children from grazing it. per ASPCA and NC State
Worth knowing
It is a cool-season annual that stalls in hot, humid summer; when it flags, shear it back, feed and water, and it pushes a fresh flush and fall rebound. per NC State and Missouri Botanical Garden
Bloom all summer, or stall?
It depends on your summers: sources report continuous bloom where summers stay cool, but a midsummer stall and fall pickup where summers are hot and humid. per Illinois and NC State
Not the native lobelias
This blue bedding annual is a South African species, not the native perennials it is confused with: cardinal flower and great blue lobelia are separate North American plants. per NC State
Frost-tender annual
Treat it as an annual: it is frost-tender and dies at the first hard frost, so most gardeners replant it fresh each year. per NC State
Deer resistant
Reported deer resistant by NC State and Missouri Botanical Garden. As with all deer claims, that means seldom browsed, not truly deer-proof. per NC State and Missouri Botanical Garden
Draws butterflies
Its flowers draw butterflies and general pollinators, though the native perennial lobelias, not this annual, are the genus's real pollinator magnets. per NC State and Missouri Botanical Garden
What pairs well with Lobelia
Good companions share its growing conditions and add something it lacks: an earlier or later bloom, a lower carpet in front, or structure through winter.
Perennial Sunflower
Takes full sun to part sun and moderate water; overlaps, then carries the display into mid fall; stands well above at 5 ft, a canopy to plant beneath; both are strong pollinator plants.
Camellia
Takes part sun to part shade and moderate water; blooms in midwinter, before this one opens; stands well above at 6.5 ft, a canopy to plant beneath; both are strong pollinator plants, and they feed in different months.
Azalea
Takes part sun to part shade and moderate water; opens in mid spring and overlaps into this one's season; taller at 4 ft, for the layer behind it; both are strong pollinator plants.
Sneezeweed
Takes full sun to part sun and moderate water; taller at 3.5 ft, for the layer behind it; both are strong pollinator plants; its seed heads stand through winter, for structure and the birds.
Globe Thistle
Takes full sun to part sun and low to moderate water; taller at 3.5 ft, for the layer behind it; both are strong pollinator plants; its seed heads stand through winter, for structure and the birds.
Winterberry
Takes full sun to part sun and moderate to high water; blooms in mid fall as this one finishes; stands well above at 6.5 ft, a canopy to plant beneath; both are strong pollinator plants, and they feed in different months.
Rosemary
Takes full sun to part sun and low to moderate water; opens in early spring and overlaps into this one's season; taller at 3.5 ft, for the layer behind it; both are strong pollinator plants.
Switchgrass
Takes full sun to part sun and low to moderate water; overlaps, then carries the display into mid fall; stands well above at 5 ft, a canopy to plant beneath; both are strong pollinator plants.
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