HEDGE MUSTARD

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.

HOW TO CONTROL IT

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.