Water celery

What does it look like?

Water celery is a perennial herb in the carrot family, Apiaceae. It’s a sprawling, emergent perennial aquatic plant that can grow over a metre in height. Plants have glossy, bright green leaves and white flowers that grow close to the leaf bases.

Water celery grows in shallow ponds and lakes, drains, canals, ditches, the margins of slow-flowing streams and riparian zones, in marshy areas and around springs. It can form submerged patches in slow-flowing deep water. Seedlings contribute to its spread from the edges of existing stands, and new populations establish from detached shoots that readily develop roots.

Why is it a problem?

Water celery contributes to the degradation of water quality in streams, especially in combination with farm drainage entering these systems. Infestations trap nutrients and deplete dissolved oxygen when plants decompose, and they threaten endangered native species in wetlands.

In the North Island, water celery needs to be regularly managed to clear drainage networks. If the weed is not cleared from slow-flowing streams, the build-up of plant biomass reduces water flow and can lead to flooding. Water celery is currently controlled mechanically and chemically, which only provides temporary relief, with rapid regrowth of surviving plants or recolonisation through seed germination.

Control methods

Can be controlled manually, mechanically or herbicidally depending on situation. Please contact us on for advice controlling aquatic weeds on watercourses – 06 835 9200.

More information

Scattered distribution from Northland to Wellington, abundant in many areas. Has also established in the north and west of the South Island.

Related links

• Landcare research article
• NZPCN listing and pdf
• Envirolink feasibility study for biological control
• Managing water celery case study