There is a week in May when bare Derry ground decides to become a lawn, and it is worth being present to watch it happen. NEW HAMPSHIRE HYDROSEED LLC works that turn — hydroseeding new and thin lawns, laying green slurry across raw grade, then the overseeding, patching and lawn care that carry it toward real turf. Rain coming off these hills does half the job; the rest is timing and attention. Nothing in this state grows on a schedule you set, only on one you meet. By July a yard that was mud in April is thick enough to cross barefoot, which is the entire idea.