How to Grow Cardinal Flower
Lobelia cardinalis
Cardinal flower thrives in moist to wet soil and part shade to full sun. Plant in spring beside streams, ponds, or in bog gardens where the soil stays consistently damp. Mulch the crown in winter for extra protection in colder areas. Plants are short-lived perennials but self-seed freely. Divide clumps every 2-3 years to maintain vigour. The brilliant red flower spikes attract hummingbirds in mid to late summer.
Yearly Lifecycle
Care Essentials
Light balanced feed in spring as new growth emerges. Avoid over-feeding which promotes weak leafy growth at the expense of flowers.
Watch For
- Slugs on young growth in spring
- Rust on leaves in humid conditions
- Crown rot if soil is poorly drained in winter
Companions
Astilbe, Ferns, Ligularia, Iris sibirica
Pet Safety
Care Requirements
Light
Part shade to full sun
Grows well in part shade to full sun. In hotter climates, afternoon shade helps prevent wilting. Full sun is fine if soil stays consistently moist.
Watering
Moist to wet soil at all times
Requires consistently moist to wet soil. Native to streambanks and will not tolerate drought. Ideal beside ponds, streams, or in bog gardens. Water deeply during any dry spell.
Fertilizing
Light spring feed
Apply a light balanced fertiliser in spring as growth emerges. Avoid heavy feeding which produces leggy growth and fewer flowers.
Pruning
Cut back after flowering or in spring
Remove spent flower spikes to prevent excessive self-seeding, or leave them if you want new plants. Cut all dead stems to the ground in late autumn or early spring.
Spacing
30 cm apart
Space plants 30 cm apart in drifts for best effect. They form basal rosettes and spread by self-seeding rather than running. Divide clumps every 2-3 years.
Support
Usually self-supporting
Flower spikes reach 60-120 cm but are usually sturdy enough without staking. In very windy or shaded sites, a discreet support may help.
Growing Tips
Never let the soil dry out
Cardinal flower is a streamside plant. If the soil dries even briefly in summer, leaves wilt and may not recover. Mulch heavily and water in dry spells.
Short-lived but self-sowing
Individual plants live 2-4 years. Allow some flower spikes to set seed and new rosettes appear at the base each autumn.
Spacing & Planting
| Plant spacing | 30 cm |
| Row spacing | 40 cm |
| Mature height | 90 cm |
| Mature spread | 30 cm |
