Roundup to kill invasive tree

johnstaci(Z5/6 NW MO)September 2, 2007

I have a few large thorny locusts on my property that I would like to kill - for safety reasons. For those of you that have never seen one, they have thousands of 2-5" thorns from the base of the trunk to the tips of the branches. They are great for mower/tractor tires as well... I will likely wait to cut them down, but want to kill asap them to keep them from spreading - they are very invasive and often sprout via suckers and from spread of their seeds.

I've heard drilling holes in the trunk and filling with concentrate Roundup will do the job. Question is, should I do this in the fall or spring, or does it matter? I remember a converstation on this board about timing based on what direction the sap is flowing. Does it really matter that much?

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Ortho Brush-B-Gone will work better than Roundup. It's best to do it just as the leaves start turning color, but not after. The sap will will start flowing down and hopefully carry the chemical with it down to the roots.

    Bookmark   September 2, 2007 at 6:48PM
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I'll second the vote for Brush-B-Gon or Pathway/Tordon - and recommend doing a frill or girdling cut all the way around the trunk, then applying the herbicide. Now is the time to do your application, as trees are 'moving' reserves to the root system for next year's spring flush of growth.
With most any, if not all of these herbicides, you need to apply to the cambium layer - drilling a hole and filling it is a waste, as application to the (non-living, lignified) heartwood does nothing. Only application to the functional, active cambium tissues will result in translocation of the herbicide to the roots.

    Bookmark   September 3, 2007 at 11:39AM
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Honeylocust doesn't tend to sucker.

    Bookmark   September 3, 2007 at 2:09PM
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johnstaci(Z5/6 NW MO)

Well, around here they do. My parents locust up in SE Iowa suckers like mad as well. I did a quick search on this forum and found others have this problem as well.

Thanks everyone for the help. I was planning on making my drill holes almost parallel with the bark (not to deep, just into the cambium). That way the tree can soak it up over a longer period of time. Will let you know if it works - should know by next spring. Can't wait to get rid of those things. I'm surprised you don't hear about more injuries from these trees.

Here is a link that might be useful: suckers

    Bookmark   September 3, 2007 at 2:30PM
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Carrie B(6B/7A)

Yeah, they sucker around here, too.

    Bookmark   September 3, 2007 at 2:44PM
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Heck, roundup doesn't even barely kill grass and weeds. Look for the ingredient "TRICLOPYR", usually in stump killers etc.

    Bookmark   September 3, 2007 at 4:01PM
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johnstaci(Z5/6 NW MO)

I was planning on using the roundup brush killer which has some triclopyr, but will definatley look to see if the other products mentioned have a higher concentration of it. Thanks.

    Bookmark   September 3, 2007 at 5:35PM
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Yes, I remember that link. The discussion was about a different species that is also called locust, Robinia pseudoacacia.

    Bookmark   September 3, 2007 at 7:54PM
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johnstaci(Z5/6 NW MO)

lkz5ia- You may not have witnessed honey locust suckering, but I can assure you honey locusts do sucker - it appears they are variable and not every tree suckers. The majority of them I have seen do- some extremely bad. My parent's thornless honey locust cultiver is extremely bad. Dozens of suckers every year. However, the thorney suckers provide the most headaches. They can't be pulled as they are full of thorns shorty after they sprout.

Here are a few more links where these suckers are referred to.

Here is a link that might be useful: HELP! honey locust tree taking over my lawn!

    Bookmark   September 3, 2007 at 9:09PM
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I've seen plenty of suckers coming from the roots of Gleditsia. And the herbicides mentioned will work, but glyphosate (Roundup) will as well, and is considerably safer for the applicator. We've also used Garlon as a cut stump treatment, such as when we're eradicating buckthorn.

Roundup barely killing weeds and grass? dead do you need it to be? I must have sprayed thousands of gallons by now, and I can assure you, the end result in every case was the death of the target vegetation.


    Bookmark   September 3, 2007 at 9:28PM
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