Lobelia Siphilitica, Blue Cardinal Flower: Gorgeous Blue Flowers July To September

Lobelia Siphilitica

Photo Compliments of Elizabeth

Lobelia siphilitica or blue cardinal flower typically grows in moist to wet locations along streams, sloughs, springs, swamps, meadows and in low wooded areas.

This is a clump-forming perennial which features light to dark blue, tubular, 2-lipped flowers with the three lobes of the lower lip appearing more prominent than the two lobes of the upper lip. Flowers arise from the upper leaf axils forming a dense terminal raceme atop stiff, unbranched, leafy stalks typically rising 24 to 36 inches in height.

Finely-toothed, lance-shaped, light green leaves (about 5 inches in length).

How To Make Your Lobelia Siphilitica, Blue Cardinal Flower Thrive

Your blue cardinal flower can easily be grown in rich, humusy, medium to wet soils in full sun to part shade; it does need constant moisture. It will tolerate full sun in cool, northern climates, but otherwise appreciates part shade.

General Lobelia Siphilitica, Blue Cardinal Flower Information

Pests and Diseases

This is a very robust plant; there are no serious diseases or insect problems.


Lobelia Siphilitica

Photo Compliments of rockerBOO

Divide clumps in spring as needed. This plant will self-seed in optimum growing conditions, forming attractive colonies.

Garden Uses

Provides late summer bloom for the perennial border, wild garden, or native plant garden.

Quick Information

  • Family: Campanulaceae
  • Common Name: Blue cardinal flower
  • Plant Type: Herbaceous perennial
  • Hardiness Zones: Zones 4 to 9
  • Height: 24 to 36 inches
  • Spread: 12 to 18 inches
  • Bloom Time: July to September
  • Bloom Description: Blue
  • Sun: Full sun to part shade
  • Water: Medium to wet (plant in the right location)
  • Maintenance: Low
  • Tolerates: Deer, heavy shade, wet soils

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Seed collection for your Lobelia siphilitica, blue cardinal flower

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  1. I have had lobelia in hanging baskets

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