Controlling Winter Grass during winter

Author: Stefan Palm   Date Posted: 19 June 2018 

Winter grass or poa annua is a what I would call a very persistent and relentless weed in Australia, particularly Southern Australia. Its that light green, seedy grass that invades your lawn during winter - the question is - how do you control it?

The word Poa means it’s from the blue grass family and the word annua means it’s an annual weed. The common name “winter grass” comes from the fact that this weed only comes up in the winter time. When temperatures get cool enough, winter grass seeds germinate then stay alive until the Spring when it gets too warm for it to survive. At this point, winter grass weeds die all by themselves.

You’d think that this would make winter grass a fairly insignificant weed but anyone who has waged war against these little blighters will know that they have a secret weapon to ensure their survival and that weapon is their seed!  Each winter grass weed can produce anywhere from 20 to a hundred seeds in its short life. That may not sound significant but picture this – One winter grass seed germinates in early winter. It grows, produces 50 seeds and then dies in the spring with all of those seeds falling to the ground. The next winter, those 50 seeds germinate and produce 50 seeds of their own. Now you have 2500 weeds. It doesn’t take long before your back lawn becomes a sea of winter grass during the winter.

It’s not all doom and gloom though – there are 2 ways that you can tackle this weed. One way is by using a post emergence control method whereby you attack it when it has already germinated. There is a selective herbicide called David Grays Winter Grass Killer which you can spray it all over your lawn and it will only target the winter grass. It contains a chemical called Propyzamide which will selectively control winter grass in couch and buffalo lawns. It does this two ways: 1) by surpressing its ability to produce seed and 2) by killing the weed but only while its young. Once a wintergrass weed matures, its very hard to selectively control.  The other (and in my opinion more successful) way of blind siding them is to use a pre-emergence method. This is where you use a chemical to kill the seed before it gets a chance to germinate. Pre-emergent herbicides (such as Pendi Pro and Embargo) only deal with seed and will not have any effect on living plants so the time to do this is the summer time when there are no winter grass weeds present. By applying these chemicals then, you ensure that the seed dies meaning there is nothing to germinate next winter. (when researching these chemicals, make sure buy the right one for your lawn. Not all chemicals can be used on all lawn types)

My advice…. Hit them with Winter grass killer now and back that up with some Pendi Pro or Embargo in the summer to make sure they don’t come back.

Comments (1)

Winter grass

By: on 22 June 2018
Thanks - good reading I used your pre-emergence fertilizer and as a result we have only small patches of winter grass this year - sharing your knowledge is much appreciated Also I have a chemical POCHECK --should this be sprayed now and does it need watering. It was recommended by our grounds manager at our golf club I am unsure if it is a pre emergent or if it kills the weed. Many thanks

Paul Munns Instant Lawn Response
Hey Des. Thanks for the feedback on the Pendi Pro. For even better results or when you have a heavy infestation of Winter Grass, you can apply a second application 6 weeks after the first. I had a look at Poachek - its made by a company called Campbells and has and active ingredient called endothall. Following is some information copied from the product label: "This product (Poachek) is a selective post emergence herbicide formulated specifically for the control of winter grass. If used on turf heavily infested with winter grass it is important that a programme of sprigging and reseeding be carried out after the treatment. This product is not persistent in the soil and reseeding can take place 2 weeks after application. Large areas of dead winter grass may form a thatch that may be conducive to spread of turf diseases and it is important that a preventative disease control program be carried out also. Do not use when temperature exceeds 25°C. Do not use on Red Fescues or Kikuyu." I would recommend that you spray it now (or whenever winter grass weeds are present)

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