I rooted the cuttings last spring and planted in the ground this spring. This is what it looked like before I did the damage.

This is it this morning.

As you can see no more grass but not much growth compared to the other cutting next to it which as I said was started and planted the same time. This one is even going to flower this year. I did the same to both - fertilized with slow release in April, miracle grow in May and alfalfa tea in June. Debating now if I should fertilize this month - if I do I will go organic slow release for sure. Thanks again for any advice.

Looks like the stunted one has a bud?? Should catch up eventually. Roundup is by no means a permanent entity. These are what, limelights? Prune each to equal sizes once they have filled out. They should grow at equal rates next year provided they receive similar treatment and nutrition. Try slow release fert with weed control for flower beds instead of instant killer.

You are right Springwood, there is a bud! I didn't realize this until you pointed it out. I had to go out and check for myself to be sure. Ha! With all the stress this plant has been through, it still will flower! I hope you are right about the roundup damage not being permanent. Yes, these are limelights. I have experience with these plants and know how well they do when pruned in late winter/early spring. But I hesitate to prune next year as I am trying to increase the height to provide privacy from the neighbor. This is why I am concerned with the stunted growth this year. No one to blame but myself. I will probably smother weeds with newspaper and shredded leaves next spring instead of putting anything down. Once a month fertilizing seems to work so I will do this again next year. Once the temp comes down, I will do one more round for this year but use slow release. Thanks so much!

Hah, no problem... Bloom-wise your cuttings are way ahead of my 5-year so by rights I should actually be jealous. Mine has microscopic buds and my little lime has ones like your stunted specimen.

Thanks again Springwood. If I can be so bold as to give advice to you, I would recommend the once a month fertilizing program for the limelight. In the past, I just gave mine a shot in the spring - usually something like composted manure or alfalfa tea. And I was happy with the results. But since I was interested in stimulating growth on this hedge I read up on a fertilizing plan and most recommendations were once a month until July or August. Not counting my roundup faux pas, my limelights did well this year.
I thought about trying the little lime but I don't have much room left in my yard. I still may try them in the future though. I have heard they don't flower the same as limelight. Is this true? Thanks again for you input.

Hey I'm no expert, just a hydrangea enthusiast undertaking a lot of testing and experience sharing. You are correct, as I only fertilized once with basic MG Shake n Feed this year. I could stand to do it in a few more spots, and now would be the last time I would do it before fall.

Little lime seems to have darker foliage and the flowers do seem to develop a little differently. I think this plant is a winner in most gardens!