Greenhouses are wonderful places, especially in the spring when benches are filled with brilliant green starts, and in the summer, its doors and roof vents propped open, with cucumbers trailing from the ceiling and tomatoes ready for picking. But in winter? Not so much. Overwintering herbs and potted plants cluster together for warmth. A few brown, leafless cucumber vines hang from an overhead trellis. Kale and spinach are over-picked and the seeds you planted have yet to sprout.