Growing Guide
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Lobelia, Great Blue

Herbaceous Perennial Flower, Wildflower

Also known as Big blue lobelia, Blue cardinal flower
Lobelia siphilitica
Lobeliaceae Family

Similar to Cardinal Flower (Lobelia cardinalis), except this short-lived perennial bears long-lasting bright blue flowers (instead of red) atop 2- to 3-foot-tall plants. Native to wet areas in the eastern U.S., requires part shade and consistent moisture for best performance.

Site Characteristics
  • part shade

Soil conditions:

  • requires damp soil

Hardiness zones:

  • 4 to 8
May be only marginally hardy in Zone 4.
Plant Traits

Lifecycle: perennial

Tends to be short-lived.

Ease-of-care: moderately difficult

Height: 2 to 3 feet

Spread: 1 to 1.5 feet

Bloom time:

  • late summer
  • early fall

Flower color:

  • blue
  • white

'Alba' and 'Albiflora' have white flowers.

Foliage color: medium green

Foliage texture: medium

Shape: upright

Shape in flower: flower stalks with upright spikes

Special Considerations
Special characteristics:
  • non-aggressive - Self-seeds, but not aggressively.
  • non-invasive
  • native to North America - Wet areas in eastern U.S.
Growing Information
How to plant:

Propagate by seed, division or separation - Sow seeds as soon as they are ripe. Self-sows readily. Some varieties may not breed true.

Make stem cuttings in midsummer.

In fall, divide new rosettes that form to the side of parent plants.

Maintenance and care:
Deadhead to improve appearance and encourage rebloom. Because plants are short-lived some reseeding is desirable.

Pinch back if you want bushier, more compact plants.

Keep soil moist during summer dry spells. Afternoon shade is beneficial if soil is dry.

Do not cut plants back in fall. Mulch lightly. While moisture-loving during the growing season, excess moisture can kill plants overwinter.

Divide plants every 2 or 3 years. Allow plants to self-seed to replace short-lived plants.

More growing information: How to Grow Perennials

Slugs and snails
Leaf spots
'Alba' bears white flowers.

'Albiflora' bears white flowers.

'Blue Peter' bears light blue flowers and may be longer-lived.