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Nutgrass – A tough little nut to crack!

Nutgrass – A tough little nut to crack!

Copyright: yogyogi

Copyright: yogyogi

Cyperus rotundas better known as nutgrass is a bother for avid gardeners all over the globe. In the USA, you might hear of purple nutgrass or purple nutsedge, or in South Africa, Wintjiekweed or red grass, Teki in Indonesia or Motha in India. As you can see, us Queenslanders are not the only ones dealing with this little green shoot and is actually commonly referred to as the “world’s worst weed!”

There is no doubting this little weed is a pest for the gardener and landscaper but it doesn’t end there! Nutgrass has been known to shoot through thick asphalt as well as pierce through pool liners in various parts of the world; there just seems to be no stopping this little guy!

Identifying the Problem

The reddish-purple colour of the flower spikelets is one of the best ways of identifying nutgrass from other weeds and grasses. But that’s only if you allow it to grow to a size where it produces its spikelets. Quite often nutgrass is found sprouting out of a recently laid lawn and in those situations it can be identified by its rapid growth and stronger, stiffer upright blades. The nutgrass will generally grow faster than the lawn and be clearly taller.

I’ve never had it before!

Nutgrass is a thrifty and persistent little weed. It has been shown that nuts can remain dormant or inactive in soil for up to 10 years. There have even been reports of nuts up to 30cm below the surface in heavy clay soils shooting after being disturbed by vehicle movement. The weight of a vehicle shifts and cracks the earth allowing water and oxygen deeper into the soil.

Nutgrass growth is severely restricted by shade. Most other weeds and many larger crop or landscape plants can eventually dominate nutgrass, but rarely will they completely suppress it. Nutgrass will almost always persist if not adequately controlled due to its complicated interconnected network of underground rhizomes (stems). Nutgrass grows most rapidly in full sunlight when adequate nutrients are available. It becomes more serious when allowed to grow without competition from other plants and this can occur when annual weeds are removed manually or by herbicide, crops are harvested or the topsoil is cultivated or disturbed for new plantings.

As stated above, nutgrass only competes well in perfect growing conditions. It is for this reason that infestations are often noticed for the first time when we spend a little time in our gardens. Fluffing up, cultivating or improving the soil, importing new rich fertile soil, fertilising, weeding, removing old plants and heavy watering are all activities that can disturb nuts and encourage them to shoot.

Generally speaking, nutgrass nuts would very rarely be transported within commercially produced planting media. This is due to the fact that most soil blends are finely screened as well as aged and heat treated in large wind rows prior to arriving at the point of sale. This process would also expose the nut to optimal growing conditions many times over before finally landing “on the shelf”.

Control and Management

The best approach for avoiding a nutgrass problem is to prevent establishment of the weed in the first place. Once established, nutgrass plants are difficult to control. You can prevent establishment through the use of manual and chemical control methods. Remove small plants before they develop tubers, eliminate the wet conditions that favours growth, use fabric mulch in garden beds (geo fabric), drying and shading. In cases where the above methods are just not possible, like in a new lawn or heavily planted garden bed, control can also be achieved using properly timed applications of specialty herbicides.

Glyphosate (Group M Herbicide) is the common ingredient in many store-bought herbicides and is often marketed as Zero or Roundup. Although touted as being a kill all weed killer, some studies have shown Glyphosate to yield mixed results when used on nutgrass infestations. However, according to a report from the Cotton Catchment Communities carried out by the NSW DPI, Glyphosate can translocate within the sprayed nutgrass plant and attached tubers.

This translocation means that glyphosate can kill the nutgrass plant it is sprayed on as well as attached tubers and nuts through underground rhizomes. The best results have been seen on fully established nuts already displaying their coloured spikelets typically over 4 weeks old.

This is obviously great news, but remember, glyphosate is not selective! Everything it directly touches will also be poisoned. For situations where overspray can cause collateral damage, like in the home lawn a group B Herbicide with the active constituent Halosulfuron-Methyl or more commonly known as Sempra should be used. Sempra inhibits acetolactate synthase, a key enzyme in the plant’s metabolic pathway. This inhibition stops plant growth and plant death occurs 14 to 21 days after initial application. Sempra does not persist for long in the soil, with a half-life of up to 34 days. Unlike glyphosate, it is reported that Halosulfuron-Methyl does not translocate throughout the attached tubers, so multiple applications may be required if the infestation is particularly advanced. In many cases, a one-off treatment is sufficient.

Crack it Before it Cracks You

So there you have it, nutgrass is a tough little nut to crack and a headache to many around the world. However, a nutgrass infestation is not the end of your garden, nor should it cause you endless sleepless nights and weekends battling the weeds in the garden. They key is to stay ahead of your nemesis and not to let it take over an area with the intention to spray it later. Best practice is as soon as you see any sign of a shooting nut attack it with a dose of Sempra (remember, Sempra is a SELECTIVE poison used to treat specifically nutgrass and as a bonus, Mullumbimby couch). As long as you treat new infestation early, Sempra should be your weapon of choice!

Remember, seek quality when shopping for your garden products! Here at Centenary Landscaping Supplies we guarantee our soils don’t come with nutgrass and if for some reason you have a nutgrass issue after using our products, let us know! We will do everything we can to investigate the ‘root’ source and help you treat the issue if it was in fact imported with the top soil.

November 24th, 2014|21 Comments

21 Comments

  1. RD March 24, 2015 at 5:53 pm - Reply

    Good advice. Thanks for the tips on Nut Grass

  2. Ashley Fiddes August 3, 2015 at 8:25 pm - Reply

    Great tips. Thanks for sharing!

  3. Ron December 31, 2015 at 5:41 am - Reply

    What is the best wetting agent to use with sempra

    • CLSOnline December 31, 2015 at 10:43 am - Reply

      Hi Ron,

      Amgrow and Searles both make wetting agents that would be suitable to use with Sempra. Although they are not necessary. Sempra is designed to work when the mist comes in contact with the grass itself and does not need to penetrate the soil. Wetting agents can also help the spray to adhere to the grass though. A shot of morning fresh (or similar) dish washing liquid per 9 Litres will do the same job in this case.

      Cheers,

      James

  4. William March 6, 2016 at 2:15 am - Reply

    This is one of the best articles on the control of Cyperus sp.
    I live in Odessa, Texas and am doing online research to see what is out there for nutsedge eradication.
    Thanks.

  5. Gary March 19, 2016 at 4:56 am - Reply

    Several years ago I applied a non-selective herbicide to small patches of nutgrass on irrigation farmland. It sterilised the soil for quite a while but eradicated the nutgrass and prevented it from being spread by tillage implements. I can’t recall the chemical. Can you help me?

    • CLSOnline March 21, 2016 at 10:39 am - Reply

      Hi Gary,

      The chemical you may be referring to is Simazine. It remains active in the soil 2-7 months after application and is generally non-selective. Alternatively, there are products marketed as ‘Once a year pathweeders’ which remain active for up to 12 months also and are based on a Glyphosate formula. Be sure to use caution when dealing with these long lasting products, as it may render an area of earth unusable for a long period.

  6. Michael September 1, 2016 at 7:43 pm - Reply

    I’ve just had new buffalo turf put down. It’s only been down for about a week and I have nutgrass coming up. What would be the best way to deal with this? This turf is still very soft underfoot so I don’t like walking on it too much. Just out of curiosity I’m wondering how it got there? Came in with the turf? Was there before the turf was laid and is just coming through? The yard was just a mess of weeds before the turf so I can’t say whether it was there before hand.

    • CLSOnline September 1, 2016 at 8:05 pm - Reply

      Hi Michael,

      The best way to tell where it came from is to peel a corner of the new turf back up and check. If the nut grass has grown from below the grass level it should be fairly obvious. Dig down to find a nut. It can occasionally come in the turf. Farms treat for this type of weed regularly but it can sneak through. As outlined in the article though, cultivating old soil, adding nutrients and water can encourage dormant nuts to grow. Treatment will be the same regardless, a dose of Sempra should take care of it for you. Did you purchase the turf from CLS?

      Cheers, James

      • Michael September 1, 2016 at 10:16 pm - Reply

        Nup. I’m not sure where it came from other than to say a turf farm in Townsville. I’m not in any hurry to find out exactly where as that would involve speaking to the gardener who I’m not particularly happy with for other reasons. Bottom line is its there so I’ll just have to get rid of it. Thanks for your advice. Now to find out the ins and outs of Sempra. LOL. Thanks again.

      • Di October 22, 2017 at 10:24 pm - Reply

        Hi James,

        I have nutgrass grown rapidly over a patch of buffalo turf (3 yrs old, sir walter from memory and most like from CLS?) that had turned brown at one stage. Turf is now back green and healthy but the nutgrass have grown stronger too. I remove them every fortnight by hand and I just can’t keep doing so as it’s really hard to dig down to it’s root. It’s growing faster than I can pull them and recent wet weather isn’t in my favor.

        Can you let me know what I can do to get rid of them completely from my buffalo turf? I always have yates weed and green which rids all other weeds but never worked on nutgrass. So frustrated.

        • CLSOnline October 24, 2017 at 2:42 pm - Reply

          Hi Di,

          I would recommend Sempra as mentioned in the article. Your general weed killer and weed and feed will do nothing to Nutgrass. Sempra should do the job for you.

          James

  7. Noel Wright September 7, 2016 at 11:16 am - Reply

    Hi, James
    I have been battling this horror for a couple of years now, and local Nurseries and hardware stores couldn’t tell me what it was. I have painstakingly, on hand and knees slowly but surely dug them out, (hundreds of them), but some still persist. I will take your advice and buy some Sempra and give it a go. I have tried every other type of weed killer, like weed and feed, with no luck. Thanks for the advice, and will let you know how it works for me.

  8. Zoe Head October 1, 2016 at 9:38 am - Reply

    Hi

    We have nut grass in a bed of soil that has been sprayed with Sempra – can we plant vegetables in that same soil –

    Thanks

    • CLSOnline October 3, 2016 at 4:24 pm - Reply

      Hi Zoe, I have done some hunting around for an answer to your question and I have not been able to determine how long Sempra stays active in soil. My suggestion would be to contact Nufarm directly for a better answer. Sorry, I would hate to give you wrong information.

  9. Gerard December 13, 2016 at 8:36 am - Reply

    I have a small nutgrass problem so I used undiluted Glyphosate and mixed in a bit of dish detergent and food colouring. The detergent helps the herbicide to stick to the leaves and food colouring to help see where Ive applied it.
    With a paint brush I sat down and painted the nutgrass leaves with this mixture and within two days I could see the nutgrass dying back.

    • CLSOnline December 13, 2016 at 8:50 am - Reply

      Using food colouring to see where you’ve been is a great tip Gerard. Glysophate is certainly the most effective treatment but there will always be collateral damage unless you are careful like you.

      As Glysophate translocates between nuts it should take care of most problems in one treatment, all it takes is some patience!

  10. Cheryl March 8, 2017 at 10:42 am - Reply

    Cheryl 8th March 2017

    We did have nut grass in our yard and we sprayed it an got rid of it years ago, but after a severe hail storm last year it has come back quite vigorously.

    I have bought Sempra but my question is if I get the spray on other plants will it kill them like Glysophate. Thank you

    I also like the tip about the food colouring to see where you have sprayed.

    • James McCullough March 23, 2017 at 8:45 am - Reply

      Hi Cheryl, generally speaking, Sempra is a selective herbicide designed specifically to kill only nutgrass (there are a couple of other uses, such as Mullumbimby couch). You should try to avoid over spray when applying any chemical, but there should be no collateral damage. As I said, take some care to limit the amount of overspray, and only treat the affected areas. Cheers, James

  11. Mick March 30, 2017 at 8:19 pm - Reply

    Thanks James. We recently excavated under our house in Eumundi Sunshine Coast which was built in the 70s. The mainly clay soil was used to build up the front yard and after a few weeks of sun and rain up came the nutgrass. It’s everywhere and I will now try your suggestion of Sempra or else be consumed by the stuff.

  12. Soraya April 13, 2017 at 2:15 pm - Reply

    Hiya, I used Sempra after much painful thinking ( I don’t like using any poisons normally). Still no yellowing after 2 days?? How long before you see it die. Maybe the food dye and detergent will help. Wondering if I should redo it. I have So so so much thick nutgrass and it drives me literally nuts… Thank you.

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