Propagating Lemna trisulca (Star Duckweed)

How to multiply Lemna trisulca, a submersed star duckweed of branching translucent fronds, through frond budding and division — and how to keep its rapid spread under control.

Overview

Lemna trisulca, the star or ivy-leaved duckweed, is an aquatic plant of the arum family (Araceae). Its fronds are oblong-lanceolate, up to about 14 mm long, blunt at one end and tapering to a tail-like stalk at the other. Unlike most duckweeds, many fronds stay connected to each other at once, forming branching, star-shaped chains.

Also unlike its surface-floating relatives, it normally grows submerged, just below the water surface, and only rises to float when flowering or fruiting. This makes it a useful low-key cover and biofilm host for shrimp and fry tanks.

Propagation Method

Duckweeds grow mainly by vegetative reproduction: two daughter plants bud off from the parent frond. Lemna trisulca multiplies the same way, through frond budding and division, which lets it colonise new water very rapidly. Simply dividing the chains gives you new plants — no flowers or seeds are needed.

Step-by-Step

Scoop out a healthy chain of interconnected star-shaped fronds.
Pinch or pull the chain apart into smaller clusters; each cluster with a few fronds will bud and grow on.
Place the divided clusters into the destination tank, letting them settle just below the surface.
Keep surface flow gentle so the submersed fronds are not blown into a single corner.
Within days, fronds bud daughter plants and the colony re-establishes.

Conditions for Healthy Growth

Lighting: low light is sufficient.
CO2: not required.
Temperature: an optimal duckweed range of roughly 20–28 °C suits it well.
pH: tolerates a wide range, with better growth around pH 6.5–7.5.
Nutrients: a modest, low nutrient demand drawn from the water column.

Maintenance

Because it can spread fast, scoop out surplus fronds regularly to keep the colony at the size you want and to stop it shading other plants. Removed clusters are ready-to-use propagation stock or a protein-rich snack for fish and shrimp.

Common Challenges

Runaway spread: rapid budding can overrun a tank — thin it on a routine schedule.
Mixing with surface duckweed: keep it separate from floating Lemna minor, which is harder to remove once mixed in.
Drifting into corners: surface or filter flow can pile the submersed chains up; ease the current for even coverage.