Propagating Proserpinaca palustris 'Cuba'

How to propagate mermaid weed Proserpinaca palustris 'Cuba' by cuttings, including the high light, CO2 and iron it needs for saw-tooth leaves and orange-red colour.

Overview

Proserpinaca palustris 'Cuba' is a locality form of mermaid weed, a flowering plant in the watermilfoil family (Haloragaceae) from freshwater swamps, marshes and pond edges of North America, the Caribbean and Central America. It is commercially cultivated for aquariums, where it stays smaller and grows more slowly than in the wild.

The species shows heterophylly: submerged leaves are deeply divided into fine, comb-like linear segments, while emersed leaves are simply serrated and broader. Stem colour ranges from green to pink, and in the tank the plant runs from greenish to orange-red.

Propagation Method (Cuttings)

Mermaid weed is propagated by cuttings. Cut and replant the top of the stem, and replant any side shoots that sprout from the base; doing so generally produces a tidier bush. The 'Cuba' form is propagated the same way as the species.

Step-by-Step

Select a healthy submerged stem with feathery, comb-like leaves.
Cut the top 5 to 10 cm with clean scissors.
Strip the lowest 2 to 3 cm of fine leaves from the cutting.
Plant the bare base into nutrient-rich substrate.
Leave the base to sprout side shoots.
Cut and replant the side shoots to build a tidier, denser bush.

Conditions for Healthy Growth

'Cuba' is demanding. It needs high light — around 300+ µmol PAR with a stronger red/blue spectrum — to reach its best orange-red colour, plus high CO2 and good nutrient availability. Without these the plant grows thinner and smaller. Strong iron and a nutrient-rich substrate support the colour. High light and warmth also trigger transitional submerged leaf forms.

Trimming & Maintenance

Trim roughly every ten days to keep the form tight. Cut and replant the tops and side shoots; this both propagates the plant and produces a tidier bush. Remember the leaf dimorphism: cuttings grown emersed carry simple serrated leaves and will switch to the fine comb-like submerged form once settled underwater.

Common Challenges

Green instead of orange-red — not enough light, CO2 or iron.
Thin, stunted stems — low CO2 or nutrient availability.
Leaf shape changing after planting — normal dimorphism as emersed shoots convert to submersed leaves.
Slow growth — expected; the species grows more slowly in aquariums than in nature.