May is the month a yard will let you change its mind. WOW Landscape And Design uses that window — laying out beds, shaping the planting, setting the lines a small Mount Vernon lot will hold all summer, then keeping them with weekly mowing, trimming and edging. A front yard here might be twenty steps across, which makes design a question of proportion: one good bed, one honest border, even grass between them. Cleanups clear the slate in spring and close it out in fall. The city is brick and stone and close-set porches, and a little green, well arranged, travels an unreasonable distance.