Gardeners instinctively know that flowers and plants are a continuum and that the wheel of garden history will always be coming full circle.  – Francis Cabot Lowell   There is something magical about a roof garden.  Parks and backyard gardens are wondrous places, but when they are placed high above the earth on a rooftop, where they are not supposed to be, the experience becomes invigorating and unforgettable.  In a