Pasture weed watch
Get on the couch
AS MUCH as I enjoy my vege garden, I have to admit I’m not very good at gardening. I grow amazing vegetables, but I have a habit of stuffing it up. Like the time I brought clubroot fungus in on my gumboots and ruined my garden for all brassicas. Or the time I applied some foliar fertiliser and accidentally used my herbicide spray tank. Not pretty.
One of my worst mistakes was the time I accidentally introduced a particularly nasty weed to my pristine garden. I sourced some free topsoil from a farmer client and subsequently spread couch through all my plots. It has been years and I’m still paying the price on that one.
Couch ( Elytrigia repens) is pronounced ‘cooch’ and is a nasty little grass weed found nearly all over New Zealand. It’s tricky to work out where exactly it’s from because it has effectively spread all over the world but it’s probably native to Europe and Asia. It’s a member of the grass family and closely related to wheatgrass, for those of you unlucky enough to have had a health food smoothie.
Now is a good time to point out that some of you will be scratching your heads and saying “that’s twitch, not couch” and you’d be right… sort of. It depends on where you come from. I’ve only ever known it as couch so that is obviously the right answer!
Some of you might be saying that couch isn’t a weed, and technically you are right. In some parts of NZ it is used as an animal feed (as it grows when nothing else does) and it does make a nice lawn grass. However put it in a crop, or a garden or a good performing grass paddock and you have yourself a nasty little weed.
As with all grass weeds, identification can be really tricky. Thankfully there are some little clues to help with the identification. Couch normally strikes in the spring but can get going nearly all year round. What sets it apart from most other grasses is that it comes away from a rhizome, an underground stem. This is what makes couch an effective coloniser and also makes it tricky to control. Stems pop off the rhizome and quickly establish themselves as tufted grass plants. These subsequently flower and produce a seed head almost identical to ryegrass and very different from all other grass species.
How to control it
This is the very meaning of futility. If you try and pull it you had better make sure you’ve got every single last piece of rhizome or it will regenerate the plant. To make matters worse, those rhizomes have a habit of hiding in amongst the roots of other plants. If you try and mulch it, you will break the rhizome into many little pieces and each one can become a viable plant. The final option is spraying. You can let the plants get a bit of size and use glyphosate. This is quite effective but non-selective. In crops you can use selective grass killer herbicides and in pasture you can’t use anything. The only advice I can give is maintain a healthy pasture sward and don’t let couch into your paddock. Be vigilant if someone is bringing agricultural machinery onto your property, don’t bring in topsoil unless you are certain of the source, and you may find it invades if you bring in gravel for driveways too.