Kohlrabi leaves are edible. A cook may use kohlrabi leaves in similar ways as she would use spinach, kale or collard greens by frying them in oil or simmering them in soups or stews.
A recipe at MarthaStewart.com calls for kohlrabi bulbs and leaves in addition to onions, butter, heavy cream and seasonings. The cook softens cubed kohlrabi bulbs and sliced onions in butter, then adds shredded kohlrabi leaves. When the greens wilt, she stirs in the cream and allows the mixture to simmer briefly before adding salt, pepper and nutmeg to taste.
Kohlrabi leaves keep for approximately three days in the refrigerator. It is advisable to wrap them inside damp paper towels before placing them in a plastic bag to retain freshness.