The good and the bad weed

NZ Lifestyle Block - - Contents -

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.

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