Lobelia cardinalis (Emergent)

Lobelia cardinalis is a North American native that grows naturally as a riparian marginal plant along stream banks and wet meadows, and its emergent form reveals its true spectacular character: tall upright stems bearing large, bright-green ovate leaves topped by blazing scarlet flower spikes up to 60 cm tall that are irresistible to hummingbirds and butterflies in open-top paludarium builds. The transition from its subtle aquarium form to this bold emergent plant is one of the most dramatic plant transformations in the hobby.

Grown emergent in paludariums, L. cardinalis is a straightforward plant with few demands beyond adequate light and moist roots. It is a perennial that dies back in cooler conditions and regrows vigorously in spring. Its flowering period is a seasonal highlight that justifies including it in any open-top paludarium with a riparian character.

Light: High; 3,000–8,000 lux; full flowering potential requires strong light or direct outdoor sun in open tops. CO2/Humidity: No CO2; roots in water or saturated substrate; stems in open or humid air. Fertilisation: Weekly balanced fertiliser during the growing season; high phosphorus encourages prolific flowering. Placement: Plant in deep substrate at the waterline; allow stems to grow tall and unsupported, or stake in windy positions. Propagation: Basal offsets after flowering; stem cuttings in saturated substrate during the growing season.