NZ Lifestyle Block - - Pasture Weed Watch - Why is it a weed? Where is it found? Is it toxic? Al­ter­na­tive uses? MILTON MUNRO Photo: H Zell Wiki­me­dia Com­mons

I’m al­ways amazed by the ge­o­graph­i­cal vari­a­tion in com­mon weed names that some­times oc­curs. I can un­der­stand there be­ing a dif­fer­ence be­tween us and other parts of the world - dif­fer­ent cul­tures and all that - but of­ten we have dif­fer­ent weed names be­tween the North and South Is­lands, or even smaller ar­eas.

For ex­am­ple, spurrey. We don’t know what that is in South­land as here it’s known as yarr, or bry­done weed. Most of the rest of the coun­try knows it as wild radish.

Last time I was in the Waikato I was taken to a pad­dock of wire­weed which - long story short - wasn’t wire­weed. Yes, it was thin and wiry, but it was a to­tally dif­fer­ent beast called hedge mus­tard, this month’s topic.

Hedge mus­tard ( Sisym­brium of­fic­i­nale) is an an­nual weed found all over New Zealand, although it is most com­mon through the Waikato and Bay of Plenty. It’s orig­i­nally from Europe and North Africa but you’d have to look pretty hard to find a place that hasn’t been colonised by this plant. It’s a mem­ber of the Bras­si­caceae fam­ily, which in­cludes broc­coli, cab­bage, swedes and, of course, the mus­tards.

Hedge mus­tard is re­lated to the mus­tard fam­ily, but it’s not a ‘true’ mus­tard - slightly

MILTON MUNRO is a soil and plant sci­en­tist for ru­ral sup­ply com­pany PGG Wright­son. He looks at com­mon pas­ture weeds you’ll find on your block and how to deal with them. con­fus­ing I know. It’s a bit of a pain in pas­ture as stock won’t eat it and it can re-seed pretty easily and spread across the farm rapidly. As with most bras­sica fam­ily mem­bers, it is ed­i­ble and in some parts of Europe it is cul­ti­vated for its leaves and seeds. I’m told it has a bit­ter cab­bage flavour.

It can be ei­ther very hard or very easy to iden­tify in the field depend­ing on the stage of its life­cy­cle. It can ger­mi­nate at any time of the year but mostly tends to emerge in au­tumn or spring. Upon ger­mi­na­tion it forms a small rosette of dark green, deeply-lobed leaves, flush with the ground. At this point in time it can be very tricky to iden­tify as it looks sim­i­lar to other rosette­shaped weeds like sow this­tle, shep­herd’s purse, the cress fam­ily and other bras­si­cas.

Soon af­ter the rosette forms it be­gins to pro­duce a flower stem and this is when iden­ti­fi­ca­tion be­comes easy. The stem is thin, pur­ple and wiry (this is why it’s con­fused with wire­weed) and it looks and feels like wire. The ends of the stems pro­duce a se­ries of small yel­low flow­ers, which upon fer­til­i­sa­tion form small green seed pods that grow par­al­lel with the stem.


Con­trol of hedge mus­tard can be a bit of a mixed bag. If you are re­mov­ing it by hand it’s eas­ier to wait un­til the flower stem forms. This gives you some­thing to hold onto - just make sure you re­move it from the pad­dock or gar­den as it can drop seed and re-in­fest your pas­ture.

If you want to spray, the likes of Tropo­tox Plus or Pre­side are great pas­ture op­tions that are clover-safe, but you have to get your tim­ing right: spray it as a seedling, when there’s no more than 4-6 leaves and cer­tainly no sign of a flower stem.

If you have a weed that is giv­ing you grief, don’t for­get to drop me a line and I will do what I can to help.

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