Skip to main content

Plants We Love: Great Blue Lobelia (Lobelia siphilitica)

For blue flowers in late summer, plant great blue lobelia (Lobelia siphilitica), a cousin of the more widely grown cardinal flower (Lobelia cardinalis).
  • Author:
  • Publish date:

Common name: Great blue lobelia

Botanical name:
Lobelia siphilitica

Lobelia siphilitica

Virtues: Blooms in late summer. Flowers are lavender to deep blue. Related to cardinal flower (Lobelia cardinalis), which has similar flowers in red.

Flowers: Tubular flowers on 2- to 3-foot tall stems. Lavender to deep blue in color.

Habit: Clump-forming herbaceous perennial, 2 to 3 feet tall and 1 foot wide.

Season: Late summer, for flowers.

Origin: Wet woods, stream banks and marshes from Connecticut through the Midwest, lower Great Plains and upper South.

Tolerates a wide range of light level, from full sun to shade. Most tolerant of full sun in cooler climates. Requires wet or moist soil. Forms clumps that can be divided and sometimes spreads itself by seed. Easy to grow if provided the damp conditions it prefers. USDA Zones 4 to 9.

Read about other blue-flowered plants

Read how to best site blue-flowered plants

Image attribution