Here are some pictures of the ground cover variety of of SJW under and between a pine and willow tree. I wanted to pull it all up and replace it with some shrubs that would be more compatible with the area and easier to maintain, but my wife has a sentimental attachment to them because her mother planted them there 30 years ago (before we met). It has not been maintained all those years except for recently when I got tired of looking at some of the invaders, like some holly, boysenberry vines and one or two other unknown wild plant life.
I did some searching around about them and found some info from our local gardening celeb, Ciscoe Morris. He said when he was working at Seattle U., they used to take a mower to them at the beginning of the season (I guess he means spring) and they would still grow back by the end of the season (I assume that means late summer or fall). Seems backwards to me, mow them in the fall and let them winter and grow back the following spring, which is what I plan to do. My wife wants me to wait until after they bloom anyway. I have weed-wacked the front edge of it a few times in the past, and they did grow back, but now I want to get at all the unwanted invaders (boysenberry vines, et al) and clean out the accumulation of pine needles and willow leaves. For now I just did the front edge and around a rock that was almost completely hidden. There used to be daffodils in the mix, but I haven't seen them lately. SJW has some medicinal qualities to it (mood enhancer), but I'm not sure if it's this type of SJW, or the other taller type, or both. Either way, I'm not inclined to harvest it for that. It does flower at least some, but I've never paid much attention to it until now. I'll post another picture when I think it's at it's peak.
I don't know what the ground was like when they were first planted, but the ground you described sounds just like the area on the side of our house that I've been working on. Compact, dry, a lot of small roots.
The picture below was taken about the same time last year at 1:30 in the afternoon. I think that's the most sun it gets, my next picture isn't until 4pm. By then it's entirely in the shade.
