Crush a leaf from one of the California bay laurels that crowd the creeks of the Berkeley hills and the air turns sharp and peppery, a fitting namesake for Bay Tree Design Inc. The business pairs lawn care with design in a city of terraces and steep, winding lanes, where the Rose Garden steps down its hillside like an amphitheater. Below it, Codornices Creek runs cool in the shade, and the streets around it reward a careful hand: lawns tucked between stone stairs, borders that have to follow a slope rather than a straight line. Bay Tree Design brings a designer's eye to that kind of ground, mowing and edging so the green reads cleanly against everything around it. In October, when the afternoon light turns honey-colored on the brown-shingle houses, coming home to a trim lawn is a small pleasure.