Some lawns in Stuart don't care whether spring is bone-dry or August is drowning, because they are synthetic grass, laid flat and green in every month. SYNLawn West Palm Beach installs those artificial lawns in a riverside town whose sandy ground drains in minutes and whose summer storms arrive almost on schedule. The real work is underneath: the ground graded and compacted, the seams joined until they disappear, the edges tucked tight along the walk and the bed line. Out near the water, where light comes off the river in sheets, the finished turf keeps the shade of a fresh palm frond from January to December. It is a different kind of lawn for this coast, and done right it seems to have simply grown there.