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Great Blue Lobelia (Lobelia siphilitica)

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A moisture-loving native perennial with upright spikes of vivid blue flowers from midsummer into early fall. Great Blue Lobelia brings beautiful late-season color to rain gardens, pollinator gardens, pond edges, and consistently moist borders while supporting bees, butterflies, and hummingbirds.

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Image credits

Lobelia siphilitica - Great blue lobelia — Fritzflohrreynolds, CC BY-SA 3.0. Resized Wikimedia Commons copy; WordPress generates additional resized display copies.

Lobelia siphilitica native distribution — Rideout Gardens; data: USDA NRCS PLANTS; boundaries: Natural Earth, Public-domain source data. Original map rendered from USDA state/province native records and Natural Earth boundaries. Retrieved October 10, 2026. Regional overview; presence is not uniform throughout shaded regions.

Great Blue Lobelia is an upright, clump-forming perennial native to eastern North America, including Maine. Its leafy stems are topped with showy clusters of blue to violet-blue, two-lipped flowers that provide valuable color and nectar from July into October.

This is an excellent choice for rain gardens, woodland edges, pond borders, naturalized plantings, and other areas where the soil remains moist. It performs well in partial shade and can also grow in full sun when supplied with consistent moisture. Plants gradually form manageable clumps and may self-seed in favorable conditions.

Plant Details

  • Growth habit: Upright, clump-forming herbaceous perennial
  • Mature size: Approximately 2 to 4 feet tall and 12 to 18 inches wide
  • Bloom color: Blue to violet-blue
  • Bloom season: Midsummer through early fall
  • Light: Partial shade to full sun
  • Water: Medium to high; prefers consistently moist soil
  • Soil: Fertile, loamy soil with good moisture retention; tolerates occasionally wet conditions
  • Hardiness: USDA Zones 4 through 9
  • Wildlife value: Provides nectar and pollen for bumblebees, other long-tongued bees, butterflies, and hummingbirds
  • Best uses: Rain gardens, pollinator gardens, native borders, woodland edges, meadows, and pond or stream margins

Full-sun locations should not be allowed to dry out. This plant is intended for ornamental use and should not be ingested.

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