There are many plants that actually thrive in a colder climate, especially with your edible varieties. Tatsoi is an Asian leafy green that can tolerate a light frost, while parsnip, leek, radish, kale and chicory are all winter-hardened veges. Just make sure you provide a layer of mulch to help keep the soil warm and your plants happy.
You can protect vulnerable plants from frost is by building light, cloth covered frames around them. Other plants should be moved inside or under cover where they still have access to sunlight.