French Hill stacks its houses close and its lawns steep, small green shelves held up by retaining walls and a good deal of stubbornness. DelleChiaie Landscaping is at home on that kind of ground — trimming what a mower can't reach, edging along the granite curb, carrying the clippings out rather than leaving them to yellow on the steps. In June the whole hill smells cut and the shade under the porches goes cool. Lawn care done street by street is how a neighborhood keeps its shape. The work runs across Leominster and out into Fitchburg, Lunenburg and Sterling.