I've been using the local soil so far which is highly regarded by the local vegetable farmers as a well-draining sandy loam. Very little clay. I have also had soil tests done revealing healthy mineral levels with the exception of Calcium and Sulfur. Healthy for growing vegetables that is. So I add Gypsum and it's all good... in the vegetable garden... during the warm, dry season.
Seems like Semps have different requirements and furthermore are perennial, having to deal with all four seasons. So far I think this soil has been more than adequate and I haven't had any issues even when I run the sprinklers or we have rain. But the Semp garden wasn't started until early July and things have been pretty dry and toasty this year. Constant cold and moisture are to be expected in a Pacific Northwest winter and spring.
Is good-draining soil enough? This soil is raised up about a foot with porous rock walls and will have no pooling during rain with the possible very temporary situation during a heavy downpour. But the soil will retain substantial moisture during cool rainy periods. The gravel in this picture is locally available and reasonably priced. Should I mulch with it? Should I tuck it under the Semps? Maybe just work it into the soil surface? Or forgo it altogether?
For the curious, that's S. Nico in the picture at the bottom left, with Amanda and the Rose Queen trying to squeeze into the picture. Ladies... please!
All courtesy of the good folks at Perennial Obsessions.