How do I kill grass under landscaping pond stones?

| March 22, 2013 | 2 Comments

Question by Pecard: How do I kill grass under landscaping pond stones?
I have a ring of pond stones around a large rosebud tree. Probably 10-12 feet in diameter. I used that black “screen” looking stuff and made sure to have it thoroughly covered. I then laid a good layer of pond stone on top of it. Looks gorgeous, but each year, more & more grass breaks through that black stuff and sticks out through the rocks. Will Round Up kill the tree itself, or as long as I’m careful, will it be OK to take out the grass?

Best answer:

Answer by Amy R
Yikes – I would not trust the round-up not to at least stunt or sicken that tree! No, I think you need to pull those grasses up and try to overseed farther away from that area or stop your grass from going to seed. The problem is that anything you use to kill that grass might kill that tree – depending on how sensitive it is and how shallow the roots are. Next time – lay down two layers of newspaper before you add the black stuff – that will buy you more time. It could also be that the pond rock it not blocking enough light and the UV rays are deteriorating the weed-blocker screen. The screening is more of a dirt-blocker than a weed-blocker anyway – it stops the dirt below from swallowing your nice pond rocks. If you wanted to stop grass, you would use a solid plastic – but that would kill the tree, perhaps, since they take in air and water through those roots and black plastic might thermalize them along with the grass if it was exposed for any serious period of time even during installation. You might want to put a layer of mulch on the screen and put the pond rock over that – that way at least if you need to pull grass, it would be growing from the mulch and it would be easier to pull.

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  1. josh says:

    if its gravel plants can grow in it no matter what i use in my garden heavy black plastic

  2. Dragon says:

    I’ve never seen Roundup devour a tree yet! You could spend forever pulling the grass up especially the running type which is almost impossible to remove by hand especially from around rocks, every viable root regrows the top again.

    Having said that Roundup will kill your tree if you are not careful. Orchards use it all the time for maintenance. Here are some choices, for you:

    If you just covered the area around the tree with weedmat and did not kill the grass before you started, you may be better to remove the pond stones, remove the weed mat spray carefully, leave the required 24 hours etc and re-weedmat and re-stone, then make sure you regularly poison the edge with round up so no more runners get into the area.

    Your other alternative is to keep a maintenance poisoning on the edge areas, then using an ordinary paint brush use straight round-up and paint the grass leaves that are poking through the stone. This will take a while and a few goes but believe me I have removed couch grass like this that I had been pulling out for years beforehand.

    Round-up is a systemic herbicide and if you paint the leaves it takes the poison to the roots and kills them to, completely killing the plant that is touched.

    If you are worried about the tree be careful not to allow any spray drift to take round-up to the leaves or trunk. (spay on a still day, and very low to the ground). Anything you cover will not be effected – you can cover the trunk with Cardboard while you spray it to protect it. (this also works in garden beds where you only want to remove a small plant from amounst others) The trick is to keep Roundup off any plant you want to keep.

    If you have an accident and touch something by mistake rinse the plant immediately. Roundup washes off, and doesn’t kill through the soil only the leaves. (We’ve had some nasty incidents at our place and all plants have lived to tell the tale). Hope this helps.

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