Cardinal Flower (Lobelia cardinalis): decorative, hardy plant for aquariums, outdoor tubs, and ponds
A versatile plant: submerged or emerged
Lobelia cardinalis is a remarkable amphibious plant that can grow both underwater and above water. In an aquarium, its soft green oval leaves (sometimes reddish depending on conditions) create 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 fall. It’s a real all-rounder: aquarium, outdoor tub, or pond—anything goes!
Why choose Cardinal Flower?
- Easy to grow in a natural or low-tech aquarium (no CO2 required).
- Versatile: submerged or emerged, aquarium, outdoor tub, pond.
- Bright red flowers outdoors (wet bank plant).
- Hardy outdoors: tolerates severe frost (down to about −22 °C).
- Easily forms a bushy growth (new shoots emerge from leaf axils).
- Ideal for creating contrasts in shape and color in aquascaping.
Planting and growing tips
- Plant in a clump (several plants) for a strong focal effect.
- Simple substrate (fine or coarse sand) is sufficient. Vigorous roots.
- Medium to high light: warmer colors (reddish) under intense lighting.
- Pruning and replanting: take side shoots or cut off the tops and replant them to make the planting denser.
- Outdoors: plant on a very wet bank or in shallow water. The rhizome withstands cold and severe frost.
Possible uses
- Low-tech aquarium: midground or foreground plant with visual structure.
- Summer outdoor tubs: robust growth, easy to adapt, and spectacular flowers in late summer.
- Ponds and damp banks: tall stems and decorative late blooms.
- Emergent plant beds (open tank or paludarium): a very attractive transition between water and air.
FAQ - Cardinal flower (Lobelia cardinalis)
Is CO2 necessary?
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 takes on beautiful reddish hues.
Is it suitable for beginners?
Absolutely: steady growth, easy care, and easy to trim.
Can it be used in an outdoor pond?
Yes. On a damp bank, it grows tall and blooms bright red in late summer. It tolerates frost and stays outdoors through winter.
How do you propagate it?
By taking cuttings (cutting and replanting the stems) and allowing the axillary shoots to grow into a bush.
Additional information
- Scientific name: Lobelia cardinalis
- Plant type: Hardy amphibious aquatic plant in our climate.
- Lighting: Bright light for a beautiful reddish hue, though moderate light is enough otherwise.
- Temperature: -22 to 28°C. It tolerates both cold and heat.
- Size: Up to 1 meter tall in a pond, shorter in an aquarium (15 to 40 cm).
- Packaging: 1 rooted plant (approximate weight: 10 g).
- Guarantee: No rock wool or any kind of artificial substrate.
- 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.
