One comment on pH which I just learned today, and want to share..
The American Community Gardening Association conference is meeting in Chicago this weekend, and I sat in on a "soils and the city" panel this morning. It was solid info presented by colleagues whom I greatly respect (Michael Webb, Dr. Shemuel Israel, and Mattie Wilson). When asked about soil pH, Michael Webb said he quit bothering about it years ago when he figured out that plants are more than capable of adjusting the surrounding pH, provided that they are already getting the right nutrients and that there is plenty of soil biology going on (read - organic matter and compost). He did mention it takes plants a few years to make this adjustment, but that it's not that big a deal.
As far as rocks go, I've placed them around berms in the fall where I had newly established trees rooting in, so that the roots would hold on to some warmth. In the spring I moved the rocks somewhere else. On a large scale, moving heavy rocks around isn't going to work out, but around particularly sensitive or valuable specimens it might be worth while. Thanks to @kctomato )tweet tweet) who first gave me the idea.
