Cardinal flower (Lobelia cardinalis): a decorative, all-terrain plant for aquariums, summer tubs and ponds
A versatile plant: submerged or emersed
Lobelia cardinalis is a remarkable amphibious plant capable of growing both underwater and above water. In an aquarium, its light green oval leaves (sometimes reddish depending on conditions) provide an ideal focal point in the foreground or midground. Outdoors, it transforms: tall stems, bushy growth, and, above all, spectacular bright red flowers from late summer through autumn. It is a true all-terrain plant: aquarium, summer tub or pond, it thrives in them all!
Why choose Cardinal flower?
- Easy to grow in a natural or low-tech aquarium (no CO2 addition required).
- Versatile: submerged or emersed, in aquariums, summer tubs or ponds.
- Brilliant red flowers outdoors (a wet-bank plant).
- Hardy outdoors: tolerates even intense frost (down to approx. −22 °C).
- Forms a bush easily (new shoots develop in the leaf axils).
- Ideal for creating contrasts in shape and color in aquascaping.
Planting and cultivation tips
- Plant in a clump (several plants) for a strong focal effect.
- A simple substrate (fine or coarse sand) is sufficient. Vigorous roots.
- Medium to high light: warmer, reddish colors develop under intense lighting.
- Pruning and replanting: take lateral shoots or cut and replant the tops to make the planting denser.
- Outdoors: install it on a very damp bank or in shallow water. The rootstock withstands cold and intense frost.
Possible uses
- Low-tech aquarium: midground or foreground plant that adds visual structure.
- Summer tub: robust growth, easy adaptation, and spectacular flowers in late summer.
- Ponds and damp banks: tall stems and decorative late flowering.
- Emersed planting (open-top tank or paludarium): a highly attractive water-to-air transition.
FAQ - Cardinal flower (Lobelia cardinalis)
Is CO2 required?
No, it grows very well without added CO2 in a well-lit tank.
Can it turn red in an aquarium?
Yes, with strong lighting and stable conditions, the foliage develops beautiful reddish hues.
Is it suitable for beginners?
Absolutely: steady growth, simple maintenance, and easy pruning.
Can it be used in an outdoor pond?
Yes. On a damp bank, it grows tall and produces bright red flowers in late summer. It is not bothered by frost and remains outdoors during winter.
How can it be propagated?
By cuttings (cut and replant the stems) and by allowing the axillary shoots to form a bush.
Additional information
- Scientific name: Lobelia cardinalis
- Plant type: hardy amphibious aquatic plant in our climates.
- Light: strong light produces a beautiful reddish tint, but medium light is otherwise sufficient.
- Temperature: -22 to 28°C. It tolerates both cold and heat.
- Size: up to 1 meter tall in ponds, shorter in aquariums (15 to 40 cm).
- Packaging: 1 rooted plant (approximate weight: 10 g).
- Guarantee: no rock wool or any artificial substrate of any kind.
- Recommendation: as a precaution, please never release this plant into the wild. Even though it is present in our regions, we must protect our fragile aquatic ecosystems.
