I always plant spinach in August for a small fall crop, which then overwinters beautifully to really take off in the spring. They are as tough as dandelions, and produce abundantly even after the coldest winters here in Indiana. Right now, my little spinach plants are under 3" of snow, with temps in the single digits, but I'm confident they will offer me an early spring harvest way before what I could ever get with a spring sowing.
I'll try to take photos in the spring (and this winter if the snows melts to allow it). The plants plants look like they are snuggled close to the ground, with smaller leaves, but in the spring, they send up normal leaves and off they go! Next fall, try it... it's so easy to get a jump on the spring crop without having to work in cold, wet soil!