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My house's interlocking pavement is covered with stubborn grass (see picture).

enter image description here

I have tried hand weeding tool but it's backbreaking work and takes too much time. The grass roots are deep into interlockings. Even when I remove part of the grass, I can't get to the roots. I will water blast the pavement and the adjoining concrete driveway but I doubt that will get rid of this grass. What would be the best method to get rid of this grass?

Any helping ideas would be appreciated.

8 Answers 8

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I'm not a huge proponent of herbicides, but this is one case where glyphosate or a similar product would be very helpful to you. If glyphosate is not available or it you wish to use an organic method, I can recommend two:

  1. Cover the entire patio with cardboard, making sure that there are no areas where light can get through between boxes. Weight the cardboard so that it doesn't blow away, and leave on the area until late fall.

  2. Same as idea 1, but use thick black plastic instead.

Regardless of how you remove the grass, it will keep returning via the seams between the pavers where the pavers meet the lawn. The only way to stop this is to lift the pavers or the adjacent lawn and use something like aluminum flashing (the material that's put around chimneys where they meet the roof) sideways along the edge of the pavers. There is also the possibility that the grass has very deep roots (deeper than 4"/10 cm), which means that it can sprout from beneath the pavers.

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  • 1
    Could you salt those cracks annually? Commented Aug 20, 2023 at 12:11
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    You could, but there's a very good chance that the salt would run down the pavers into the grass, killing a portion of the lawn and sterilizing the soil until it leached out. I would not do that.
    – Jurp
    Commented Aug 20, 2023 at 17:46
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    @YosefBaskin Probably not a big deal for pavers but you can damage concrete with salt as well.
    – JimmyJames
    Commented Aug 21, 2023 at 18:29
  • "The only way to stop this is …". Once you are sure the grass is dead and completely cleaned out of the cracks, if there is an actual gap between the pavers you could fill it with Polymeric Sand. Every year or two you might need to patch any parts that have worn away or come loose, which is a lot easier than de-weeding the whole thing. See also The 6 Biggest Mistakes When Using Polymeric Sand. Commented Aug 23, 2023 at 2:58
  • @RayButterworth. Polymeric sand it great for preventing weeds from coming in from the top, but not so great at preventing weeds from coming in from the side. And as you note, you need to partially re-do the sand annualy or biennially.
    – Jurp
    Commented Aug 23, 2023 at 11:51
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I've found that boiling water will kill the grass for as long as 6 months but you'd probably want to take care that it doesn't also get on the grass that you want to keep growing.

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For my interlocking pavers I spray a liquid product that is advertised as "year long" which contains glyphosate, pelargonic acid and imazapic. It really does last for a year or more with one application.

There's a similar product with "365" in its name with glyphosate, imazepic and diquat that I've used in other years, and it works just as well.

In areas where I don't want to use chemicals, I've used a propane weed torch. For fire safety, I've only used the torch during light rain or immediately after a soaking rain. Wet weeds hiss, pop and sizzle as they die under the torch, which is particularly satisfying. (Apologies to any weed lovers.)

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Another tool is a pressure washer. You can use this as is or use glyphosate and after the die back blast the roots out.

The real key to success is to use polymeric sand afterwards to fill in the gaps and top up as required

Safety concerns indicate you should wear pants, close toed shoes and goggles while using a pressure washer

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Treat with glyphosate. After seven days use a powerful strimmer to physically remove the grass. Make sure stones, etc that may be flung far and wide by the strimmer can't damage anything (including yourself).

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There are propane torches for this kind of purpose. It will not remove the grass entirely but repeatedly wilting the grass will kill it. Take care on natural stone which can delaminate or crack if heated excessively. It's also important to avoid/protect things you want to keep like grass on the sides. The idea is not to burn the grass or other plants but cause the water inside them to burst the cell walls. The grass will turn a darker green and then collapse and die. It's therefore best to do this while the grass has been watered and/or it has rained recently. Note that spraying down grass with water will not prevent the grass from being damaged so you need to avoid, cover, or otherwise shield the plants you want to keep.

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There are different types of herbicides, but in the end if you have areas where you completely want all plants gone, in comparison to using herbicides (which are mostly selective, which you want when getting rid of weed in lawn) this works perfectly:

1 gallon white vinegar 1 cup salt 1 tablespoon liquid dish soap

Combine those in a spray bottle, apply to the whole pavement area and you will see any grass/weed will be brown within a day.

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If it's growing like that a comprehensive root system is formed underneath that cant be easily eradicated. Best solution is to dig it out and replace substrate with sand and put the paving back. If that's too severe or time consuming, a local herbicide is in order.

Lazy way is weed whack the interior grooves down to the inside.

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