The good and the bad weed

I’M REALLY interested to know who can identify fathen ( Chenopodium album) when looking at their paddock from the gateway. Unfortunately I don’t mean a plump chicken, but this annual weed that germinates in spring, can stand up to two metres tall in autumn and is prevalent throughout the country.

It was originally native to Eurasia and North Africa, but is found almost everywhere in NZ, in vegetable gardens, compost heaps, new crops, pastures and paddocks.

If fathen comes under stress (like any plant), it puts its seed head up early. This means you’ll spot fathen flowers from December-may, depending on which part of the country you are in. However, these stalkless clusters are completely covered by the floral parts of the plant, making it extremely difficult to identify and determine when the seed is about to be dropped.

Fathen does have some distinguishing features. From seedling growth, the coarsely-toothed leaves can be up to 7cm long by 4cm wide and look as though they have had a permanent dusting of icing sugar over them.

It usually germinates in spring, then grows until it produces clusters of flowers which then drop tiny glossy-black seeds in autumn. This little nasty often produces tens of thousands of seeds from each plant and every single one can remain viable in the soil for years. Fathen can also produce an extensive root system with an abundance of fine fibrous roots to continue to source nutrients and water for survival.

How to kill it

As winter approaches, frosts have the ability to kill it off.

But if you are wanting a chemical option to beat the seed drop, you can use the phenoxy range of herbicide such as 2-4D across grass paddocks. Fathen’s soft leaves make the weed highly susceptible to most phenoxy products when spraying out pasture paddocks.

If you grow crops such as maize, there are cases where fathen is becoming resistant to triazine herbicides, making it essential to control fathen at the seedling stage.