Propagating Caulerpa lentillifera (Sea Grapes)

How to propagate sea grapes, an edible marine green macroalga, by dividing its creeping stolon, with refugium and aquaculture tips and a warning about going sexual.

Overview

Caulerpa lentillifera, sea grapes or green caviar, is an edible marine green macroalga that can grow to about 30 cm. Instead of leaves it carries rounded bead-like ramuli on creeping stolons; the beads burst in the mouth with a fresh umami, ocean-like taste, and it is eaten raw in salads.

Like all Caulerpa it is a siphonous alga — a giant single cell with many nuclei. It has been commercially cultivated since the 1950s in Cebu, the Philippines, and is widely grown in refugiums for nutrient export.

Propagation Method

Sea grapes are propagated vegetatively by fragmentation and division of the stolon. Each piece of creeping runner bearing healthy beads and rhizoids will re-anchor and grow into a new clump — this runner division, not substrate cuttings, is how both refugiums and aquaculture farms multiply it.

Step-by-Step

1. Select a vigorous length of stolon carrying plump green beads.
2. Separate it from the parent by pinching or cutting the runner.
3. Place the fragment on rubble or mesh in the refugium or culture tank so rhizoids re-attach.
4. After about two months for a fresh start, then every couple of weeks, harvest the new growth.

Conditions for Healthy Growth

As a tropical marine species it needs stable marine conditions: full salinity, alkaline pH near 8.0–8.4 and warm water. In aquaculture it is grown in shallow ponds and tanks; in the reef tank a lit refugium serves the same role.

• Full-strength salinity and alkaline marine pH.
• Medium lighting on a steady photoperiod.
• Dissolved nitrate and phosphate to fuel its fast, nutrient-exporting growth.

Maintenance

Harvest on a regular cycle — farms crop it roughly every two weeks once established. Frequent harvesting keeps it actively growing, maximises nutrient export and is the best safeguard against it going sexual.

Common Challenges

The going-sexual crash is the main risk in a closed system. As with the whole genus, never release Caulerpa into the wild, since several Caulerpa species are notoriously invasive escapees from the aquarium trade.