Marsilea mutica aka Australian Water Clover

Marsilea mutica is a water fern called Australian water clover. Its other name is smooth nardoo. This perennial lives for more than one year. It belongs to the Marsileaceae family. Kew lists its native range as northern and eastern Australia, plus New Caledonia. Other sources list western Australia and Tasmania too. It grows beside ponds, lagoons, and rivers. It lives in shallow pools that come and go. It grows in deeper water too.

This fern spreads at a slow rate through long rhizomes. These creeping stems branch as they grow. Fronds rise one at a time or in groups along them. Garden plants reach about 0.3–1.6 feet [0.1–0.5 metres] tall. They spread about 3.3–4.9 feet [1–1.5 metres] wide. Useful Tropical Plants records fronds up to 3 feet [0.9 metres]. The leaves float on long stalks at the water's surface. Each leaf has four leaflets shaped like triangles. This gives the leaves a clover-like look. The glossy blades are dark green. Pale green marks lie near their centres. Leaves measure about 0.07–0.1 feet [0.02–0.03 metres] across. The plant sheds its leaves with the seasons.

Grow it in full sun with rich, loamy soil. The RHS suggests muddy pond edges for planting. Baskets filled with soil are another choice it gives. Keep basket planting depths within 0.5 feet [0.15 metres]. Acid to neutral soil suits it. It needs wet ground or shallow water in gardens. The RHS gives it a UK hardiness rating of H5. Plants For A Future lists USDA zones 8–11. Plants reach full garden size in two to five years.

Its floating leaves form ground cover for wet garden sites. It also suits bog gardens. It needs no routine pruning. The RHS reports few pest or disease problems. Divide the rhizomes in summer to make new plants. Peg the pieces into shallow water while they take root. It also grows from spores held in structures called sporocarps. Accounts of its food use refer to these structures.

Aboriginal Australians gathered sporocarps from wild plants to eat. Sources describe cooking the spores, then grinding them into starchy flour. Yet they are astringent and hard to digest. Sporocarps contain thiaminase, an enzyme that breaks down vitamin B1. Eating large amounts can cause grave health problems. Thorough drying or cooking can reduce this enzyme. These steps may not remove it, though. Useful Tropical Plants thus treats it as emergency food. It does not treat it as a staple food. The supplied sources record no medicinal uses.