Mediterranean oregano, the essential ingredient in Greek salad, and Italian pizza and pasta sauces, grows wild on the mountains of southern Europe. Its strong, sweet flavor elevates the taste of garlic, lemon and tomatoes. The stronger and less sweet Mexican oregano works well in spicy dishes such as chili and salsa. It is also sometimes called "common oregano."

Dried oregano, either preserved from your garden or purchased at a grocery store, is dark green and crumbly, making it easier to measure than fresh leaves. The more concentrated flavor means you need less to achieve the same effect, typically a 3:1 ratio. For example, if a recipe calls for 1 tablespoon of fresh oregano, use 1 teaspoon of dried oregano instead. Crumble oregano in your fingers to release the oils before adding it to your recipe.

Fresh oregano leaves should be bright green and supple, without damage, mold or spots. Wash and blot the leaves dry just before you use them. Store extra leaves, unwashed, with a damp paper towel in a plastic bag in the refrigerator for up to five days. Throw away leaves that turn pale or yellow.

With an oregano plant at home, you can harvest the leaves as you need them, though they're most flavorful just before flowers bloom. Freeze leaves in an airtight container for later use, or dry entire stems by hanging them in bundles upside down in a dark, dry place for two weeks. Crumble the leaves onto a tray and store the crumbs in an airtight container.