Marsilea drummondii aka Common Nardoo

Marsilea drummondii, or common nardoo, is a fern from Australia. It is native there and grows across the mainland. It belongs to the fern family Marsileaceae. Its range spans warm temperate zones and the tropics. Kew places it in climates with a dry season. Wild plants grow in mud and shallow water, even in the mountains. They also grow in still water and slow streams.

This fern lives for years. It reaches about 1 foot [0.3 metres] tall. A long stem, called a rhizome, creeps through the ground. It branches often, with leaf clumps rising at points along it. The plant can carpet soil or spread across a pond's surface. Photos also show it on drier ground among taller plants. Useful Tropical Plants notes that its form can vary a lot. It has spores, not seeds. Cases called sporocarps hold the spores.

In gardens, nardoo needs wet soil or a place in water. It grows in sun or part shade. It suits sand, loam, and clay soils. The soil can be mildly acid, neutral, or mildly alkaline. Its low growth suits a bog garden. It can spread to form cover beside or across water. Plants For A Future lists USDA zones 8–11. It reports survival near 19°F [−7°C] in Australian gardens. It warns that this limit may not apply in British gardens. Britain has cooler summers and longer, wetter winters. These can change how much cold the fern can bear.

To grow new plants, use the spores in the sporocarps. Plants For A Future says to wear down the outer surface a little. Then soak the cases so they swell and split. The spores enter the water and start to grow. The first roots and shoots can appear within two or three days. Plants may form their own sporocarps within three months. These times describe how to grow new plants from spores. They do not show how fast plants spread in gardens.

Aboriginal Australians gathered the sporocarps for food. People can cook the starchy spores or grind them into flour. Sources call them astringent and hard to digest. Useful Tropical Plants warns that the sporocarps contain thiaminase. This enzyme breaks down vitamin B1 and can cause serious health problems. Drying or cooking can reduce it, but it resists heat. These food uses do not mean casual eating is safe. Plants For A Future lists no known medicinal uses.