Could you put up a white picket fence where you have the rope? Most front yard ones are about 3 feet tall.

Hoping for a plant solution if possible

Nobody can make plant suggestions unless we know where in the world you are. Australia? Austria? Alabama?

Bah sorry. Toronto Canada

A solid bed of Liriope. Does that grow there?

Sorry but no plant - unless plastic - will hold up to repeated ministrations of dog urine. If juniper can't, liriope won't.

You might post in Shrubs, Small Space Gardening, and be sure to list where you are located. This forum is more for design, rather than exact plants.

I found this when I googled, but you will have to check and see if any will grow in your area. I would go to a local nursery, not a big box store, and ask also.

https://www.hunker.com/13406544/what-plants-can-withstand-dog-urine

YMMV, but Hunker would be one of the last places I'd go to get reliable plant and garden advice. A bit like visiting Facebook to get accurate news reports............

Who do you like then? I have a mailbox post planting that I need to change out for the same reason.

Hunker was just the first that popped up. Here are all the results.

https://www.google.com/search?q=what+plants+are+resistant+to+dog+urine&oq=what+plants+are+res&aqs=chrome.2.69i57j0l7.16416j0j8&sourceid=chrome&ie=UTF-8

I don't really rely on those sorts of websites :-)

Dog urine is urea and with a high salt content. If you were to spray that, undiluted, on any plant on a daily basis it would seriously harm it and probably eventually kill it. Some plants will be more tolerant of the abuse than others but all will be damaged to some extent. It's like a high powered fertilizer overdose on a daily basis. That's asking a lot.

What seems to be the most resistant (but not immune) are broadleaved evergreens with very glossy or thick foliage - euonymus or laurel for example. The waxy surface cuticle of the leaf resists urine penetration into the plant tissue.

What I would do in this case is incorporate some landscape boulders along the sidewalk edge to keep dog traffic through the area to a minimum. Then you could fill in with some tough evergreen groundcovers or small shrubs. The shielding offered by the boulders will keep them from getting drenched daily ;-) Not exactly a plant-only solution but one that can creatively address the issue.

Thanks so much everyone. Sorry new to the site. Happy Saturday to all

No plant suggestions, sorry. My dogs will push right under a roped off area -- they just don't understand it means keep out. So you will need to fence the whole perimeter. It doesn't have to be especially tall, but must be sturdy enough that a dog understands it is a barrier.

Also, many dogs get used to eliminating on one type of surface -- either grass OR hardscape -- and won't be attracted to the other surface. Don't know your neighborhood but maybe you can use that to your advantage.

Dig Doug's suggestion above would keep my dogs from 'depositing', and looks very nice :-)