Potamogeton crispus

Also known as Curly-leaf pondweed, Curled pondweed, Curly pondweed

FreshwaterBrackishStemCuttings

Invasive. Regulated as an invasive aquatic plant across much of the United States, including as a prohibited species in Minnesota. Never release into the wild; dispose of trimmings in the trash.

Potamogeton crispus (Potamogeton crispus) — Krzysztof Ziarnek, Kenraiz · CC BY-SA 4.0

Care at a glance

Light: Low light
CO2: No CO₂ needed
Growth rate: Fast
Placement: Background
Type: Stem
Temperature: 39–75°F (4–24°C)
pH: 6.5–8.5
Hardness: 4–18 dGH
Max height: 31.5 in (80 cm)
Spread: 3.9 in (10 cm)
Nutrient uptake: Root + water column
Growth region: Submersed
Difficulty: Easy
Origin: Eurasia, Africa and Australia; introduced almost worldwide
Family: Potamogetonaceae

Overview

A plant for unheated tanks, coldwater setups and ponds rather than tropical aquascapes. It is close to indestructible in cool water: low light is enough, CO2 is unnecessary, and rooted stems grow fast enough to need regular cutting back before they run along the surface. The translucent, wavy dark green leaves read a little like Bolbitis and make a distinctive background. Warm tropical temperatures work against its natural rhythm and can push it into summer dieback, so keep it below the mid twenties. In much of the United States it is a regulated invasive, so never let fragments or trimmings leave the tank except in the trash.

In the wild

Native to Eurasia, Africa and Australia, growing rooted in lakes, ponds, canals and slow rivers in fresh and slightly brackish water, and now spread across much of the rest of the world. It is entirely submersed, with no floating leaves, and runs on an unusual cool-season clock: it grows actively under ice in winter, peaks in late spring, then dies back in high summer, leaving dormant buds called turions to restart the cycle. It tolerates remarkably low light and water as cold as 1-4 degrees C.

Good to know

A pondweed in the family Potamogetonaceae; the name crispus means curled, for the translucent, wavy-edged leaves with finely toothed margins, up to about 7.5 cm long. Thin rhizomes creep through the substrate and send up long branching stems, and the plant reproduces by fragments and by its hardened winter buds, the turions. It stands out in the genus for growing wholly submersed rather than producing floating leaves.

Did you know

It grows under ice: curly-leaf pondweed tolerates very low light and starts its growing season in winter, which is exactly the head start that lets it smother native plants where it has been introduced.