Wolffia globosa aka Asian Watermeal

Wolffia globosa, or Khai Nam, belongs to the arum family, Araceae. Kew places its native range in tropical and subtropical Asia. It grows on the surface of quiet, fresh water. It also lives in water with a slow flow. Growers raise it as a vegetable in Laos, Myanmar and Thailand. Its small size makes it one of the world's smallest flowering plants.

The plant has tiny fronds that float free on water. Useful Tropical Plants gives a height of about 0.03 feet [0.01 metres]. It can form very dense groups on the surface. Recorded stands hold over two million plants per square metre. Both horticultural sources call it an evergreen perennial. Kew instead lists its life form as an aquatic annual. These sources thus differ on its life cycle.

Its flowers are small and do not make a showy display. Plants For A Future reports flowering mainly during summer. In suitable climates, flowers may appear throughout the year. The plant is self-fertile, so it does not need another plant to set seed. Growth is fast when conditions suit it. Its biomass can double within a few days. Division lets it spread without the need to sow seed.

For cultivation, the sources call for sun and still water. The water should contain ample nitrates and lime. Plants For A Future says it cannot grow in shade. It lists USDA zones 10–12. Both horticultural sources describe resting buds that help it survive winter. These sink to the pond floor in late autumn. They return to the surface in spring. Its value in ponds lies chiefly in food production and wildlife use. Aquatic animals eat it, and growers use it as fish feed. It also takes up excess nutrients from the water.

People cook the edible fronds, which the sources call leaves. Their taste is described as mild, sweet and cabbage-like. They supply protein, carbohydrates and several vitamins. Plants For A Future lists no known medicinal use. Both horticultural sources flag a possible calcium oxalate risk. This warning rests on its family, not confirmed findings for this species. Such crystals can cause pain in the mouth and throat. The sources urge added caution for people prone to kidney stones or gout. These limits matter when weighing its use as food.