My guess would be to water them plenty. At nurseries they water their stuff ALL the time so everything looks healthy and lush for customers to see. After plants get bought from these stores they still should get lots of water for a while. I've bought I don't know how many potted plants that died after I brought them home for seemingly no reason. Then I got a part-time job at a nursery where my biggest task was watering all their plants for like 3 or 4 hours a day. They'd even tell me "now water the big ones till water comes out the bottom". Yeah, the transplant shock could also have something to do with it. I always thot that the planting hole should be like 3 times the size as the root ball part.

What a great idea for that space! You might want to peruse some sites to get a visual look at the plantings others have used (see my link below). Or just study creek beds (although your plants won't be the usual 'water' plants due to dry conditions (unless you want to lay a drip line along the banks of your stream). In real creek beds I think you'll find that there are all sizes of stones from boulders to gravel, grasses and wildflowers of different heights. It sounds like your choices will have to like a fair amount of shade. Also, I would recommend laying some thick landscape cloth in the 'creek bed' prior to adding the rocks. That way any weeds that eventually form between the rocks cannot establish very deep roots and can be more easily removed. Of course a little Roundup sprayed onto weeds might be just as easy. Here is a link that might be useful: google image pages of 'dry creek beds'

AKA Himalayan Balsam. It's a giant annual. It is a major invasive pest in the UK and Ireland which takes over river banks and water margins. Quite possibly in the US too.

It has been a long while, but I remember the white berries didn't have any blue, and were larger in size and had a different flavor. If the white part was rubbed off (not easily done), or the berry opened (easier), the skin was not colored. There were blue berries that did form a whitish film, but they were obviously blue underneath. Bushes were consistent in which color berries they formed year after year. The largest plants always seemed to be of the dark-berried type, but that could have been a coincidence. My observations spanned many years, but I had no formal botanical education at that time. The area burned in several wildfires, and I have not revisited where the light colored berry bushes were seen. But since the discussion was continuing, I thought I'd add my recollections. If blackrab is willing to share a more detailed description of the location, it may be possible for me to check the plant she photographed during a future trip to San Diego County. Of course, the birds may have eaten them all or something, but throwing it out there as a possibility. I have a trip planned in 2 weeks, but I will have other people along, and don't know where the location of the plant is in conjunction to where I will be going.