In making our last garden on a steep, damp piece of hillside we
brought in a lot of material: quarried basalt rock for retaining
walls, round rock for drains, an ocean of gravel. When we moved
house a few years ago, I was aiming for a garden with a lighter
carbon footprint. Among other things, I hoped to save energy by
bringing in as little material as possible. As I learned more
about our new yard, those hopes went down the drain, so to
speak. We discovered, during remodeling, that the soil
immediately around the house is pure clay with a thin veneer of
soil. That explained why rain and irrigation water runs straight
to the bottom of the garden, where it drains into an alley and
forms near-permanent, year-round puddles. Shrubs have shallow
root systems, suckering madly and showing drought stress at the
drop of a hat. Other areas of the garden have decent soil, but
the lie of the land and impervious underlying subsoil combine to
ensure that some spots are squishy and anaerobic for much of the
year. Gray, stin