Great Blue Lobelia plant profile
Lobelia siphilitica
A perennial flower for partial sun.
Last updated .
When to plant
When to plant Great Blue Lobelia
Great blue lobelia is a clump-forming perennial that blooms from mid-summer into early fall (July to October) and may be divided in spring (NC State). A spring planting band aligns with the stated spring division window, though the page gives no explicit planting date.
The calendar shows this cited seasonal window as an approximate band. It does not convert the season into frost-adjusted dates.
Open Great Blue Lobelia in my garden calendarShows the source-backed planting season, not frost-adjusted dates.
Growing conditions
- Sun
- Partial sun
- Lifecycle
- Perennial
- Hardiness
- Zones 4 to 9Find my hardiness zone
Common problems
Watch for these
Also watch for: dry soil stress, short lived clumps.
Next steps
Continue with Great Blue Lobelia
Evidence trail
Evidence behind this profile
Original extension and institutional publications behind the planting, care, and safety facts on this page.
- Lobelia siphilitica (Great Blue Lobelia)
NC State Extension, North Carolina Extension Gardener Plant Toolbox. Supports general reference. Checked 2026-06-18.