Dennerle Lobelia Cardinalis

Lobelia cardinalis, the Cardinal Flower, is a North American native wildflower known for its brilliant red blooms in terrestrial form. In aquariums, the submerged form produces compact rosettes of broadly oval, spoon-shaped leaves in bright green on the upper surface with rich purple-red to magenta on the undersides — a striking color combination that provides visual contrast in the midground of planted aquariums.

The submerged form of Lobelia cardinalis grows differently from the emergent form: leaves are smaller, more spoon-shaped, and arranged in compact rosettes or along compact stems. Under moderate to strong light with CO2, it is an attractive, colorful accent plant that bridges the gap between typical green and red aquascaping plants.

This plant is more demanding than easy beginner plants like Anubias or Cryptocoryne but less demanding than highly specialized red plants. It requires moderate light and benefits significantly from CO2 supplementation. Without CO2, it can survive but grows slowly and the purple-red underside coloration may be less vivid.

Dennerle supplies high-quality aquarium-adapted specimens of this plant as part of their planted tank range.

Light: Medium to high light (25–60 PAR). Low light produces weak, leggy growth. Medium-high light maintains the compact rosette form and purple undersides.

CO2: Beneficial but not strictly required. CO2 injection (15–25 mg/L) improves growth rate and color intensity of purple undersides.

Nutrients: Moderate nutrient demands. Liquid fertilization with micro and macro nutrients supports healthy coloration. Iron supplementation enhances the purple-red leaf color.

Placement: Midground accent. Best planted in groups of 3–5 for visual impact. Effective as a color contrast element against green stem plants.

Maintenance: Moderate. Remove yellowing leaves. Propagate by taking side shoots and replanting. Trim tall stems to encourage branching.

Water Parameters: pH 6.0–7.5, temperature 20–28°C, soft to moderately hard water.