>> Also think drainage doesn't get enough credit.
Agreed! In my yard that's the major factor, even more significant than shade. Before amending it, not even weeds do well on my clay.
Drainage, shade & exposure, elevation, insect pests and pathogens (and probably mulch and snow cover) all make huge differences.
I think one reason I enjoy growing things is that, even if science "should" predict everything about gardening, in reality every single square yard is so complicated that teams of PhDs could labor for years trying to explain everything. And they would still be stumped by green plants without a single neuron.
P.S. here's an "Idea" about the microclimates in one backyard:
http://garden.org/ideas/view/P...
