Butterfly fern

Salvinia auriculata

Also known as Eared watermoss, Butterfly moss, Salvinia auriculata complex, African payal, Giant salvinia

FreshwaterFloatingFragmentationDivision

Prohibited. Listed as a US federal noxious weed, so bringing it into the US or moving it across state lines needs a USDA permit, and some states ban it outright. Never release into the wild.

Butterfly fern (Salvinia auriculata) — Mateus Hidalgo · CC BY-SA 2.5 br

Care at a glance

Light: Medium light
CO2: No CO₂ needed
Temperature: 68–82°F; 20–28°C
Max height: 1.6 in; 4 cm

Growth rate: Fast
Placement: Floating
Type: Floating
pH: 6.0–8.0
Hardness: 2–18 dGH
Spread: 11.8 in (30 cm)
Nutrient uptake: Water column
Growth region: Submersed or emersed
Difficulty: Easy
Family: Salviniaceae
Origin: A floating fern from the still fresh waters of tropical Central and South America, where it drifts in green mats across ponds and slow rivers.

Overview

Butterfly fern is a fast-growing floating fern that lives on the water surface. It is an easy plant.

Did you know

The hairs on the leaves of butterfly fern join at the tip like an egg whisk and hold a layer of air. That keeps the leaves dry and gives a splashed mat a silvery sheen. Engineers study the shape for surfaces that stay dry under water.

Caring for butterfly fern

Float butterfly fern on the surface in medium light, away from strong surface flow, which flips and tears the leaves. It needs no CO2. It takes its food straight from the water and pulls out excess nitrate and phosphate, so any feeding goes in as a liquid fertilizer.

Butterfly fern grows fast at 68 to 82°F (20 to 28°C), and it gives shade and cover to surface-dwelling fish and fry. Pieces that break off keep growing, so a few plants soon spread across the surface. Thin it regularly so it does not shade out the plants below or choke gas exchange at the surface.

Good to know

Butterfly fern is a floating fern in the family Salviniaceae. Each node has two rounded floating leaves that sit like tiny butterfly wings. A third, finely divided leaf hangs underwater and works like a root. It has no true roots and spreads by spores and by fragments breaking off the stem. Young plants lie flat, and crowded ones grow larger leaves that fold upright. Shops often sell it as Salvinia natans, which is a different fern from Europe and Asia.

In the wild

Butterfly fern comes from the still fresh waters of tropical Central and South America. It drifts in green mats across ponds and slow rivers.

Common questions

Does butterfly fern need to be planted in the substrate?

No. Butterfly fern floats at the surface and takes its nutrients straight from the water.

Does butterfly fern need CO2?

No. Butterfly fern grows well without added CO2.

How much light does butterfly fern need?

Butterfly fern wants medium light. A light sold for planted tanks covers it.

How do you propagate butterfly fern?

Butterfly fern propagates by fragmentation and division. Pieces that break off keep growing, so pulling a clump apart spreads it. Each plant buds off new ones, so a few soon cover the surface.