Propagating Salvinia minima (Water Spangles)

Water spangles is a floating fern that multiplies by fragmentation as daughter fronds split off the chain, growing fast — but it is invasive in the southern US and must never be released.

Overview

Salvinia minima, commonly called water spangles, is a small free-floating aquatic fern in the family Salviniaceae. It is rootless, with leaves arranged in three-part whorls: two floating green leaves and one submerged, finely dissected leaf that functions in place of true roots.

It inhabits still or slow-moving freshwater such as lakes, ponds and canals, and its floating fronds give shade and cover for surface-dwelling fish and shrimp fry.

Propagation Method

Water spangles reproduces asexually through fragmentation of its creeping stems and buds. The plant is thought to be sterile and cannot reproduce sexually, so daughter fronds split off the chain and become independent plants. Through this continuous fragmentation it shows exponential growth.

Step-by-Step

Pick a healthy floating chain carrying several leaf pairs.
Pinch or pull the chain apart into smaller fragments, each with at least one or two leaf pairs.
Return each fragment to the water surface so the floating leaves sit upright.
Let the fragments grow on; each will continue branching and budding into new plants.
Repeat whenever the mat needs thinning.

Conditions for Healthy Growth

As a floating species it draws nutrients directly from the water and needs no substrate. It tolerates a wide range of still freshwater conditions and even brackish water up to about 4 to 7 ppt salinity, passing through three growth stages from flat initial leaves to curling secondary leaves and finally dense tertiary mats.

Maintenance

Because growth is exponential, thin the floating mat regularly so light still reaches plants below the surface. Scoop out and remove excess fronds before they form a dense tertiary mat that blocks gas exchange and shades the whole tank.

Common Challenges

Runaway growth and dense surface mats that block light and gas exchange.
Spread to the wild if disposed of carelessly, given its invasive status.
Water droplets sitting on leaves, which can cause melting; the leaf hairs normally repel water, so keep the surface calm.