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Lobelia siphilitica
Species; herbaceous perennial
At‑a‑glance
- Group/Class: Species; herbaceous perennial
- Height × spread: 24-36 in (60-90 cm) × 12-18 in (30-45 cm)
- Bloom window: July to September
- Color & flower form: Blue tubular flowers in dense terminal racemes
- Fragrance: 0 none
- USDA hardiness: zones 4-9
- Breeder / Year / Origin: wild species; unknown; Eastern North America
- Pet safety: avoid
How it differs
- Baseline species for the Great Blue Lobelia group in stature and timing.
- Hardier to cold than many hybrid fan lobelias.
- Later summer bloom compared with many border perennials.
- Performs best in wetter soil than most perennials.
Strengths
- Dependable late‑season color in rain gardens.
- Tolerates wet soil and brief flooding when established.
- Low maintenance in rich, moist sites.
Care in one minute
Site and light: full sun to part shade; afternoon shade helps in hot summers.
Soil and pH: rich, humusy soil with steady moisture; slightly acidic to neutral.
Watering: keep evenly moist from spring to fall; do not allow to dry out.
Feeding: work in compost in spring; avoid heavy nitrogen.
Grooming: remove spent spikes to tidy; divide clumps in spring if crowded.
Overwintering: hardy in the region; mulch lightly only where frost heave is common.
Watch‑outs
- Needs consistent moisture; stems and foliage decline in drought.
- Foliage may be chewed by slugs and snails.
- May self‑seed in ideal conditions.
Best uses (tags)
Provenance note
A species native to eastern North America and common along streams and wet meadows.
References
- Missouri Botanical Garden Plant Finder – Lobelia siphilitica
- NC State Extension – Lobelia siphilitica
- ASPCA – Lobelia (toxicity to pets)
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