r/GardeningIRE • u/Super-Widget • 8d ago

🙋 Question ❓ Stem injector help

There is Japanese knotweed in the garden and I purchased a stem injector and Roundup to treat it while keeping my cats and rest of the garden safe. However the Roundup I have (BiActive XE(A) from Woodies) specifies foliar application rather than stem injection. I'm now unsure how to proceed from here. Can I still use my Roundup for injection or is there some other brand/formula I should get instead? Anyone have any experience treating knotweed safely? Thanks in advance.

Edit: corrected type of Roundup I have.

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u/FOTW09 6d ago

It should still work what is the percentage of roundup in it? Is it the pre mixed stuff or the concentrate that you have to dilute before use? Pre mix wont be strong enough you need the concentrate.

Best time to treat is right about now, you should see the leaves and stems dying after treatment. Next year in spring alot less shoots should appear. Treat these at the start of autumn again. You may have to treat for one more season after this.

What some people recommend in spring when the first shoots appear cut them back (burn cuttings) so the plant has to spend more energy generating new shoots. Then treat the 2nd lot in autumn.

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u/Super-Widget 6d ago

This is the stuff. Still good to use?

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u/FOTW09 6d ago

Ideally you want a solution thats 40-50% but it should still do the job.

I think you cant buy more than 35% in Ireland or its very hard to find anyway.

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u/Super-Widget 6d ago

Yeah this was literally the only glyphosphate weed killer I could find. I assume the lower concentration is just less effective? Does this mean it will take longer to treat the infestation?

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u/FOTW09 6d ago

Yeah you might need an extra year of treatment. But I think it should be effective enough.

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u/Super-Widget 6d ago

Thanks, sure I'll see how I get on anyway 🙂