Apium prostratum aka Prostrate Marshwort

Apium prostratum is in the carrot family, called Apiaceae. People call it sea celery or prostrate marshwort. Kew lists it as a biennial or perennial from temperate regions. It lives for two years or more in these mild regions. Its native range spans parts of southern Africa and Australia. In Australia, it grows in the south and southeast. It is also native to New Zealand and several Pacific islands. Its range includes parts of South America, too. These include southern Brazil and northeastern Argentina. It is not native to Britain or Ireland.

Plants For A Future describes a perennial, reaching 2 feet [0.6 metres]. Crush the leaves to release a strong celery scent. Wild plants grow on headlands and dunes by the sea. They also grow near brackish swamps and salty riverbanks. Such sites fit reports that it grows in salty soil. Each flower has both male and female organs. Flies pollinate the flowers. The plant is self-fertile: it can set seed with its own pollen.

In gardens, it prefers rich soil that stays moist. Give it some shade in summer. It grows in sand, loam, or clay. Soil can be slightly acid, neutral, or slightly alkaline. Plants For A Future lists it for garden beds. Its shore habitat and salt tolerance may help guide its placement. The sources give no firm rating for cold hardiness. Nor do they give dates for when it blooms. They give no fruit or garden pest details for this species.

The leaves taste salty and have a strong flavour. Use them in soup or as a garnish like parsley. You can also eat them raw. Use seeds to season soups and other dishes. Blanched stems can take the place of celery. Their small size and tough fibres limit this use. The account lists the root as safe to eat. It does not say how to prepare it. People have proposed using this plant to breed vegetables. The account records no use as medicine.

Sow seed in a greenhouse in spring. Seeds may take a month or more to sprout. Move seedlings to their own pots when large enough to handle. Plant them outside in summer. You can also divide well-grown plants in spring. People have used pads from this plant to seal canoe leaks. Take care with its sap despite its food uses. Skin contact may cause dermatitis, a form of skin rash. It may also make skin sensitive to sunlight.