Cardinalflower (Lobelia cardinalis)

How much light does a Cardinalflower need?

Cardinalflower takes full sun, part shade or full shade outdoors. Full sun is the preferred exposure, which means six or more hours of direct sunlight a day. Part shade and full shade are also listed. That gives you a choice of spots, from an open bed to a shaded corner.

• Light: Full sun, part shade and full shade (full sun preferred)^1,2,3

How often to water a Cardinalflower

The recorded water need for cardinalflower runs from medium to wet. The soil should never be allowed to dry out. Brief flooding is tolerated. Moderately moist to wet soil is described as where it grows best. No cited source gives a watering schedule in days, so judge by the condition of the soil instead.

• Water: Medium to wet^2,4

Best soil for a Cardinalflower

The recorded soil drainage is moist and occasionally wet. Soil that stays moist suits the plant, and a soil that dries out does not. Organically rich soil is the type described for its best growth. It also tolerates brief flooding. Moist and occasionally wet describe the drainage, and dry soil is not among the recorded conditions. No cited source records a preferred soil pH, so this page gives none.

• Soil drainage: Moist and occasionally wet^2,4

Hardiness and temperature

USDA hardiness zones 3a–9b are the range recorded for this plant. That range reaches from the cold end at zone 3a to the warm end at zone 9b. No cited source records a minimum temperature, so the zone range is the only cold guide here. Humidity needs are not documented either.

• Hardiness: Zones 3a–9b^2,5

How to plant a Cardinalflower

Cardinalflower is recorded for USDA zones 3a to 9b. Allow for a mature height of 4–5 ft (1.22–1.52 m) and a width of 1–2 ft (0.3–0.61 m). Its habit is erect. Choose a spot with full sun if you can, and with soil that will not dry out. No cited source gives a planting time relative to frost, so this page does not name one.

• Hardiness: Zones 3a–9b^2,5

Winter care

Cardinalflower is recorded as hardy from zone 3a at the cold end. Zones colder than 3a fall outside the recorded range. The plant type is recorded as herbaceous perennial. No cited source records a minimum temperature or gives winter protection steps, so this page lists none.

• Hardiness: Zones 3a–9b^2,5

How to propagate a Cardinalflower

The recorded propagation methods are seed, division and layering. Layering is described as bending a stem down into the mud and fastening it with a rock or sticks. Seed, division and layering are all listed, so you have three routes to a new plant. How to divide the plant, or when to sow seed, is not documented on this page.

• Propagation: Seed, division and layering¹

Common problems

Slugs and snails are the pests recorded for cardinalflower. Snails and slugs may damage the foliage. The disease recorded is tobacco ringspot virus. The virus is recorded under the name Nepovirus nicotianae for Lobelia. No cited source gives treatment steps for either problem.

• Common pests: slugs and snails²
• Common diseases: tobacco ringspot virus⁶

Questions and answers

Is cardinalflower toxic to cats and dogs?

The ASPCA lists cardinalflower as toxic to cats and toxic to dogs. No cited source on this page names the parts involved or a severity. Cats and dogs are the only animals this site covers.

How much sun does cardinalflower need?

Full sun is preferred, and part shade and full shade are also listed. Full sun is described as six or more hours of direct sunlight a day. That range lets you place it in a bright bed or a shadier one.

How big does cardinalflower grow?

Its mature height is 4–5 ft (1.22–1.52 m), with a width of 1–2 ft (0.3–0.61 m). Its habit is erect. Its flowers are red, pink or white.