By now the roundup has moved into the plants. You will see the extent of the die back in the next 2-3 weeks. With any luck you will only have affected the sprouts. With no luck the entire plant will die.

Mistakes are how we gain experience in life. At the worst you will have to replant the trees if you want to.

Good luck.

Now you know not to do that again, but in all honesty, it's near impossible to kill a crepe myrtle. I dug some up 5 years ago and there are still suckers coming up 10-15 feet from where the rootball was. With as little surface area that the suckers have compared to the tree I doubt your tree will notice.

you would .. most likely ... have to cover 40 to 60 per cent of the plant.. to significantly effect a large plant ...

i doubt you applied enough to do such ..

but it would be interesting.. if you let us know... what if any impact happens ...

snap a pic today.. so that if there is some impact.. you can show us the before and after ....

ken

Besides percent coverage, concentration will also play an important role. If you used the fairly weak pre-mixed stuff and only shot a few suckers, you may escape damage. If you applied the RoundUp to a lot of suckers and/or mixed it heavily, chances of failure go way up.

It sounds like at this point, all I can do is cross my fingers and wait... I used the premixed RU in the spray bottle, so it sounds like that may be a good thing in this case? I hit maybe a dozen suckers between 2 CM's growing about 12' apart. I will update. If I make it through the next two weeks without apparent damage to the parent trees, I presumably dodged the bullet?

If there are no signs of damage in the next few weeks, you're probably OK. But the real test is in how well the trees leaf out and perform next spring.

As of today, the suckers are still growing! A few leaves down the stems are singed, but overall, they're still going to town. Dang, they're tough!

I'm not gonna count my chickens yet, but so far, it looks like my fears may have been overblown.

I'm curious as to why you don't remove the suckers. That may be one reason you have had to fight them so much in the past; when you let them grow, they form dormant buds, which then produce more suckers when you remove the larger suckers. By ripping the suckers off when they are very small, instead of cutting them down when large, you can do quite a bit to discourage new suckers (or, to not encourage new suckers).