Description
Lobelia cardinalis, known as cardinal flower, is an upright perennial with glossy, bright green leaves. In mid to late summer it carries tall spikes of brilliant scarlet, two-lipped flowers, each about 5 cm long.
Cardinal flower at a glance
| Botanical name |
Lobelia cardinalis |
| Common name |
Cardinal flower |
| Plant type |
Clump-forming perennial; overwinters as a rosette of leaves |
| Height and spread |
Up to about 90 cm tall, about 50 cm wide |
| Flowers |
Brilliant scarlet, two-lipped, in tall spikes, mid to late summer |
| Position |
Full sun or part shade |
| Soil |
Reliably moist to wet loam |
| Pond depth |
0–5 cm of water in summer; lift out of the water for winter |
| Hardiness |
RHS H3 – hardy in mild and coastal areas only (-5 to 1°C) |
| Native to |
North America (not UK native) |
Is cardinal flower hardy?
Only in mild areas. The RHS rates it H3: hardy in coastal and relatively mild parts of the UK only. Elsewhere, lift it out of the water for winter and give it frost protection, as freezing water can damage the rosettes.
Where to plant it
- The shallow edge of a pond, 0–5 cm deep in summer
- Bog gardens with reliably moist soil
- Full sun or part shade
Is it poisonous?
Yes. All parts are harmful if eaten by people or pets, and it can irritate skin, so wear gloves when handling it. Watch for slugs and crown rot.
Which size should I buy?
Bare-root plants (7 cm, 9 cm, 1 litre and 3 litre) arrive without a pot or compost and are the most economical way to plant a group. Potted plants (9 cm, 1 litre and 3 litre) arrive growing in our peat-free compost and give a faster display. Packs of 3 come in 7 cm, 9 cm, 1 litre and 3 litre bare-root sizes and cost less per plant. The 2x Pot & Compost option is two plants supplied with pots and compost.
