Tetragonia tetragonoides

Tetragonia tetragonoides, commonly known as New Zealand spinach or warrigal greens, is a member of the Aizoaceae family. Although sometimes grown as a vegetable, in many agricultural regions, it is categorized as a weed that can rapidly colonize open spaces, roadsides, and cultivated fields, competing with primary crops.

Botanically, it is an annual herbaceous plant characterized by a prostrate growth habit with spreading, succulent-like stems. It falls into the group of summer annual weeds. The species is highly adaptable, showing a preference for sandy, moist, or slightly saline soils, often becoming invasive in irrigated agricultural lands.

The biology of Tetragonia tetragonoides is defined by its robust vegetative growth and high seed production. The stems have the ability to root at the nodes when in contact with moist soil, allowing the plant to spread horizontally and form dense mats. Its seeds are hardy and can remain dormant in the soil seed bank for extended periods, making eradication difficult.

The weed causes significant harm by outcompeting crops for resources such as water, light, and nutrients. The dense ground cover it creates can also increase soil humidity, promoting the growth of soil-borne pathogens and providing shelter for insect pests. In vegetable production, it can easily smother young seedlings and drastically reduce overall yield.

Effective control measures require a strategic combination of methods:

• Mechanical removal through frequent shallow cultivation and hoeing to sever root connections.
• Crop rotation to break the lifecycle of the weed in heavily infested fields.
• Use of weed mats or heavy mulching in horticultural systems to suppress germination.
• Chemical control using selective systemic herbicides during the early rosette stage before the plant develops an extensive sprawling network.