Never heard of oak leaf lettuce. Must only be in CA or West Coast. Oak leaf here is the tree leaf.Here in the states, "Oak leaf" refers to a type of lettuce that is sometimes put into these lettuce mixes. Its to actual oak leaves from an oak tree and its not an ivy.
Oak Leaf Lettuce: Description, Flavor, Benefits, And Uses - Gardeners' Magazine
Discover the elegance of Oak Leaf Lettuce: Savor its unique flavor, explore its health benefits, and learn its various culinary applications.gardenersmag.com