Growing ivy-leaved duckweed in a pot

Ivy-leaved Duckweed is well suited to container growing — at about 15 cm mature it is comfortably pot-sized. A container around 15-20 cm (6-8 in) across gives it room without leaving the compost sitting wet, which is the usual mistake when people over-pot a small plant.

Aim for a container 15-20 cm (6-8 in) across. Pot on when roots show through the drainage holes or growth slows noticeably — usually every 1-2 years for a plant this size. Move up one pot size only; jumping several sizes leaves wet compost the roots cannot reach, and that is what rots them.

Use a quality peat-free compost with a handful of perlite for air, and make sure the pot has drainage holes. Compost in containers compacts over time, which suffocates roots — that is the main reason potted plants decline.

Containers dry far faster than open ground, so ivy-leaved duckweed in a pot needs checking more often than the general guidance of "Permanently submerged" — especially in summer, wind, or a heated room. Check the top few centimetres with a finger rather than watering on a fixed day.