Old Tappan keeps its stone walls under the oaks, and at midday in late spring the light comes down through that canopy in coins. Biosphere Landscape Architecture works those shaded Northern Valley yards — mowing at the height the trees will allow, edging the walks so the green line stays where it belongs, trimming close along the wall stones without scarring them. Cleanups open the beds again in April and lift the heavy oak leaf in October before it can mat down over the turf. Nothing here happens fast; ground under old trees has its own pace and the work respects it. Still, the turn from overgrown to kept is a single afternoon's difference, and it shows from the road.