Myriophyllum pinnatum

Care at a glance

Overview

A fast, dense background milfoil with green to reddish stems, usually sold in bunches as green myrio. Give it at least medium light, and CO2 plus iron-rich fertilisation if you want the foliage full rather than sparse; fine-leaved stems like this show poor light as bare lower stems. It prefers the cooler end of tropical temperatures and is one of the few common stems happy in coldwater setups. Trim and replant tops regularly, since the bunch thickens from replanted cuttings rather than from old stems. The fine foliage doubles as cover for fry and shy fish.

In the wild

Native to eastern North America, growing in shallow lakes, pond margins, swamps and marshy woodland. It is amphibious, with submersed stems in open water and a stockier emersed form on wet mud. Its range runs well into the temperate zone, which is why it handles genuinely cold water and works in unheated tanks and ponds.

Good to know

A watermilfoil in the family Haloragaceae; pinnatum means feathered, for the finely divided leaves. Botanically it is easy to pick out of the genus because the leaves sit both in whorls and alternately on the same stem, where most milfoils keep strict whorls. An older synonym is Myriophyllum scabratum, and in the aquarium trade it has long been mislabelled Myriophyllum hippuroides, which is properly a different, western North American species.

Did you know

The mixed leaf arrangement is the identification trick: find whorled and alternate leaves on one stem and you are holding Myriophyllum pinnatum, whatever name the shop label uses.

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