I was off work for all of October and when I got back, between a couple more heatwaves and Round-up
2 more have disappeared.
The 1 that's left is looking pretty good. We'll see how it goes.
One thing this has shown me is that it can be done if they get some shade. The soil they're in is fairly heavy clay which I hear is okay, but I'm glad they're on a slope. The other thing I have noticed is that bunnies and sowbugs like them too.