NORTHFIELD, Wis. — Stepping into the massive greenhouse of Superior Fresh — 6 acres under one roof — the gentle embrace of warm, humid air is quickly followed by the smell of lush, green plants.
Daylight streams through the roof, and the sound of sloshing water tricks the senses into a kind of tropical reverie. Seen from nearby Interstate 94, the greenhouse at night glows purple as red and blue lights come on to help organic leafy greens grow during sun-deprived winter months....