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Glysophate and Crepe Myrtles

Posted on 6/14/25 at 10:04 am
Posted by STLhog
Dallas, TX
Member since Jan 2015
18834 posts
Posted on 6/14/25 at 10:04 am
Have gone through hell removing Asian Jasmine ground cover that surrounds one of my nice, developed crepe myrtles.

Should a few treatments of glyso on the remaining jasmine roots hurt the tree if I keep some distance?
Posted by Ricardo
Member since Sep 2016
6189 posts
Posted on 6/14/25 at 10:20 am to
From what I've been told, it's almost impossible to kill a Crepe Myrtle.
Posted by Major Dutch Schaefer
Location: Classified
Member since Nov 2011
38222 posts
Posted on 6/14/25 at 10:24 am to
quote:

Should a few treatments of glyso on the remaining jasmine roots hurt the tree if I keep some distance?


Should be okay.
Posted by Spankum
Miss-sippi
Member since Jan 2007
60559 posts
Posted on 6/14/25 at 12:07 pm to
Glyphosate must be absorbed through the leaves of plants…won’t hurt if you spray it on the roots of your crepe Myrtle
Posted by Loup
Ferriday
Member since Apr 2019
15666 posts
Posted on 6/14/25 at 1:57 pm to
I drilled holes in the stump of one and filled the holes with concentrated glyphosphate. Its still putting up shoots
This post was edited on 6/14/25 at 1:58 pm
Posted by Dallaswho
Texas
Member since Dec 2023
3394 posts
Posted on 6/14/25 at 2:52 pm to
One of the safest things you can do. And it degrades in just a couple days to a week so you can replant quickly. Just make sure it’s actually glyphosate. The new roundup formulas don’t use it anymore.
Posted by 98eagle
Member since Sep 2020
3111 posts
Posted on 6/14/25 at 4:21 pm to
EDIT: I miss read the OPs post. He is trying to kill Jasmine roots growing adjacent to his Crepe Myrtle. My response below is for killing Crepe Myrtles. One thing I will say about my experience with Triclopyr is that I had regular Nandinas growing into Encore Azalea bushes. Triclopyr will kill both. I had to basically paint the Triclopyr onto some of the Nandina leaves. Any drops that accidentally touched Azalea leaves, I immediately cut those leaves off. Three weeks later the Nandinas were dead and the Azaleas were fine. So whatever poison the OP uses, I would be super careful to not get any poison on Crepe Myrtle leaves or root suckers.


Per an AI response: To effectively kill Crepe Myrtle, consider using a systemic herbicide like triclopyr or a phenoxy herbicide such as 2,4-D or dicamba. These herbicides can target the plant's roots, preventing regrowth. You can also use sucker stoppers which are plant growth regulators.

I've used Fertilome Brush Killer/Stump Killer to kill practically impossible to kill regular Nandinas recently. It contains 8.8% Triclopyr and did the job, but it took several weeks. I had tried Tractor Supply's Glyphosphate product about a month before and it did nothing to kill the regular Nandinas.

Fertilome Brush Killer/Stump Killer has a much higher percentage of Triclopyr compared to Roundup Poison Ivy/Tough Brush Killer which has the following active ingredients:
Triclopyr, triethylamine salt ... 0.122%
Fluazifop-P-butyl ... 0.097%
Diquat dibromide ... 0.073%

I was at a Garden center that had other Triclopyr products in higher percentages than Fertilome. All were pretty expensive.

I'm not saying Triclopyr will work on Crepe Myrtles but an AI response using a Google search said it would, and Triclopyr killed my regular Nandina bushes which are as hard to kill as Bamboo.
This post was edited on 6/14/25 at 4:40 pm
Posted by STLhog
Dallas, TX
Member since Jan 2015
18834 posts
Posted on 6/14/25 at 4:39 pm to
Just trying to kill the Asian Jasmine ground cover, not the Crepe even tho it’s a lame tree. It looks decent.

Jasmine is the absolute worst. Back breaking work this morning with a chain saw, reciprocating saw and hedge trimmers. Just brutal.
Posted by 98eagle
Member since Sep 2020
3111 posts
Posted on 6/14/25 at 4:44 pm to
Yeah, I misread your post just like everyone else. I put another paragraph at the beginning of my last post. I would try Triclopyr but be super careful not to get any on any crepe myrtle leaves or sucker roots. If you have Jasmine roots and Crepe Myrtle sucker plants growing into each other I would not spray that directly. It is absorbed through the leaves and takes a few weeks to kill brushy plants.

Here is the AI response:

What chemical kills Asian jasmine ground cover?
3. Herbicide Use:
Glyphosate:
Products like Roundup (containing glyphosate) can be used to kill Asian jasmine, but careful application is crucial to avoid harming surrounding plants.
Triclopyr:
A Reddit user says they used Clear Pasture (containing triclopyr) to kill Asian jasmine, with success, while avoiding damage to trees.

Tractor Supply sells Glyphosphate.
This post was edited on 6/14/25 at 4:52 pm
Posted by Ingeniero
Baton Rouge
Member since Dec 2013
21987 posts
Posted on 6/14/25 at 8:13 pm to
I'll tell you one thing, you ain't killing that asian jasmine or that crepe myrtle with glyphosate
Posted by oldskule
Down South
Member since Mar 2016
23227 posts
Posted on 6/14/25 at 9:04 pm to
Nothing kills crepe myrtles
Posted by STLhog
Dallas, TX
Member since Jan 2015
18834 posts
Posted on 6/14/25 at 10:08 pm to
What about MSM*?

The good kind with another vowel on the end?

Might know a guy.
Posted by Tree_Fall
Member since Mar 2021
1082 posts
Posted on 6/15/25 at 9:18 am to
quote:

Nandina bushes which are as hard to kill as Bamboo


I had a nandina thicket that needed to go growing around a crepe myrtle. My yard guy struggled with it. He tried shears on the stalks and an ax on the root mat. Finally, he rented a small walk-behind stump grinder and chewed the roots out down about 6 inches. That worked to remove the nandina, and the crepe myrtle didn't seem to be impacted at all.
Posted by 98eagle
Member since Sep 2020
3111 posts
Posted on 6/15/25 at 12:59 pm to
A dense Nandina thicket is almost impossible to remove manually. I had previously tried to dig up a 20' wide and long dense Nandina group. I was digging up the root mat by brute force with a pick mattock. I thought I had it all dug out. However, even an inch of a piece of root will grow back a Nandina bush. After applying Glyphosphate failed I went to a local garden nursery and they told me to use Triclopyr. It actually worked to kill the Nandinas but it is slow. After more than a week I was about to give up but maybe in about two weeks later I could tell it was starting to work. If the Triclopyr had failed I was going to cover the Nandinas under a Tarp for a year. I had also thought about renting a Tiller to better dig up the entire root mat. It's interesting that your yard guy used a stump grinder to kill the Nandinas. I'll keep that in my memory bank.

Triclopyr is going to be my first choice to try and kill any woody bushes, trees or vines that I can't successfully get rid of manually like a cluster of Nandinas. I live on heavily wooded acreage. I usually just rip out vines or cut them down with a brush cutter. For bushes I don't want, I usually just pull them out of the ground using a come along winch and axe. I also use my Echo PAS 225 weed eater to take out thousands of new tree sprouts twice a year in the areas I don't want any more trees or any plants growing.
Posted by STLhog
Dallas, TX
Member since Jan 2015
18834 posts
Posted on 6/15/25 at 2:59 pm to
I ordered some cross bow and will give the Jasmine a dense treatment and then put cardboard down with some mulch on top.

Selling the house so will be someone else’s problem. People should think before putting some of this crap in.

The amount of time and effort I’ve put into clearing a 15x15 plot under the tree is absurd. Will look 50x better with a mulch bed.

Until the jasmine resurfaces I suppose.
This post was edited on 6/15/25 at 3:00 pm
Posted by 98eagle
Member since Sep 2020
3111 posts
Posted on 6/15/25 at 9:47 pm to
I just checked the ingredients and percents in Crossbow. That should kill the crap out of the Jasmine ground cover. Good luck with the move. Hope it all goes well for y'all.
Posted by DMAN1968
Member since Apr 2019
12586 posts
Posted on 6/15/25 at 9:58 pm to
quote:

I ordered some cross bow and will give the Jasmine a dense treatment

I've had this work though it took multiple treatments. I hit it once and after a few weeks it didn't look like it did much so I hit it again and that knocked it back hard.
Posted by dragginass
Member since Jan 2013
3182 posts
Posted on 6/16/25 at 12:31 am to
Call me crazy, I'd rather the jasmine around the tree than mulch.
Posted by STLhog
Dallas, TX
Member since Jan 2015
18834 posts
Posted on 6/16/25 at 8:12 am to
I hear you. It wasn’t properly pruned by the first owner and got too tall and was spreading badly into my best st Augustine. I kept trying to get it down but it just looked scalped and crappy. Needed a fix to make it aesthetic for listing.

Was also a ton of work keeping it off the crepe Myrtle.

Will add some native grass into the mulch bed and should look a lot better than it did,
This post was edited on 6/16/25 at 8:16 am
Posted by Warwick
Member since May 2022
1968 posts
Posted on 6/16/25 at 4:01 pm to
just fyi for the future, glyphosate alone will keep knocking the jasmine back. if you just want to play it safe. its how i control it around my banana trees
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