Pasture Weed Watch

Tarweed

A COUPLE of weeks before our paddocks are shut up for hay, I take a walk. I sprayed dock and buttercup this spring and followed it with a bit of fertiliser. That should have left the pasture looking good for a lovely hay crop to feed the cattle and horses next winter.

But on closer inspection, I found a lot of tarweed. It grows all over New Zealand, and it would seem my Hunua block, 40km south-east of Auckland, is a hot spot.

Tarweed is a flowering plant in the broomrape family. It's native to Europe, but is now found worldwide.

This annual herb grows upright to about 60cm, producing a stiff, slender stem coated in hair. It's very sticky, and I'm guessing that's how it got the name tarweed.

Its hairy leaves are lance-to-oval in shape, lined with several teeth and very prominent indented veins. The flowers are yellow and grow up the stem.

It flowers from late November to the end of January, then sets seed.

How to control it

The most effective form of control is to pull the plants out by hand. Tarweed helpfully stands out due to its height and yellow flowers; my wife and I filled more than 20 bags out of our hay paddocks last year.

There are no herbicides that specifically claim to control tarweed. Anecdotally, spraying other weeds with 2,4-D (Baton or Sprinter) when tarweed plants are small seems to kill it.

Why is it a weed? Competes in pastures and disturbed land Where is it found? Across New Zealand, usually on wet wasteland Is it toxic? Yes, believed to cause alkaloid poisoning