1. Kale
Kale is one of the hardiest greens; it loves cooler temperatures and can even be sweetened by frost. It can withstand temperatures as low as 20°F (-6°C), creating an awesome possibility of harvests into fall and early winter.
To grow kale, plant seeds or sets of kale in well-draining soil replete with organic matter. Allow the plants to receive at least six hours of sunlight per day. For harvest, pick off outer leaves as desired and let the plant's center continue to produce.