On Penn Valley’s wooded slopes, drainage and tree roots decide what can be built and what will grow.

The neighborhood is unincorporated, so there is no borough government here — Lower Merion Township handles the permits and the roads, and zip 19072 is shared with Narberth next door. The houses are mostly mid-century: split-levels, ranches and contemporaries set well back on large lots, with older stone houses mixed in among them. Streets follow the hills instead of cutting across them, and the ground falls away toward Mill Creek and, beyond it, the Schuylkill. Very little of a property here is flat and open.

Slope and canopy set the problem list. Water leaving a yard uphill arrives with momentum, so downspout runs, swales and the grade in the first few feet off a foundation matter more than they would on level ground. Mature trees mean thin turf on the north and east sides of a house, moss in the low spots, and beds laid out for full sun decades ago now sitting in shade. Roots are the third constraint: oaks and beeches put structural roots exactly where people want steps, walls and terraces.

So the work here runs toward grading and stone rather than decoration. Retaining and garden walls to hold a bank, steps that take a slope in even risers instead of one long scramble, patios on a base deep enough to sit still through a wet winter, and drainage tied into all of it. On the planting side it is more bed renovation and shade-tolerant replanting than new borders. Maintenance follows the trees: pruning, fall cleanup, leaf removal, and overseeding in September where there is light to support it. Penn Valley sits in the middle of the route, so most weeks the truck is already on one of these streets.