September in Montclair turns the light amber by four o'clock, and the deep porches on the streets near the Art Museum start looking like paintings of themselves. von Hoffmann Landscape Architecture Inc. tends the ground those houses sit on — lawns kept even and green, beds edged clean, the shape of a yard held steady through the growing season. Old properties carry old plantings, and mowing around a hedge somebody set out a century ago is slower work than open turf. Then the leaves arrive, and the leaves in this town are serious, coming down in waves until Thanksgiving. Cleared away, the lawn underneath reappears looking deliberate, which is rather the whole point.