I trench edge so don't have that quandry. In either case, you have some kind of defined boundary between bed and grass. Given my druthers, I'd edge and put rocks on dirt - but you're going to have grass growth around, under, and between the rocks anyway. I don't see that as a satisfactory edging solution if the rocks aren't large and mortared together. Then you'd only have to spend time weed whacking or hand clipping where the mower can't go.

Rachel, I used Brush Killer, undiluted. There are different brands but it will say 'Brush Killer' on the container. I believe Basic RoundUp is a different product. I see RoundUp now offers a combined mixture that supposedly kills brush, ivy, etc. too. I don't know how well it might work on stem cuttings. When I googled Brush Killer, several items popped up; Bayer Advanced Brush Killer Plus Concentrate, Southern Ag Brush Killer, etc. I think the product I used was made by Bayer. Remember not to dilute the product, just pour a bit of the product into a throw a way cup or something with a broad flat bottom where you can set it down without fear of it overturning, like an empty plastic milk container with the top cut out, anything that will work for you and can be disposed of following your work session. Soak the cotton balls and apply one cotton ball to each freshly cut stem, cover with a plastic sandwich baggie, secure tightly with a strong rubber band and you're done. Be safe. Secure the pets while you're working. Wear good hand and eye protection. I usually doubled the gloves I wore and then threw them away after each work session. Be careful when handling the product. When the weather is warm, I usually noticed wilting within a day and then over time, the plant dies and dries out. I had such a mess of these vines coming up out in my lawn and coming up in my garden beds. Nothing I tried worked until I used the cotton balls. The vines had created a garden nightmare for me. Good luck. You will be so relieved when these things die off. Mary

Thanks for the feedback, flyleft; I appreciate it. I laid out some tiles to show my husband what I was thinking of, and he liked it. it's still hard for me to visualize how a whole wall of glass tile will look topped with the stone border. Got to work on that vision thing! Loved the rock column in the link you sent.

I'd remove some of the soil on the new plants and spread the roots. But either way should be fine, as you have chosen well! Both are really strong easy going plants!! Just make sure they have good drainage and don't overwater once they are established. Where is NEO??