The easiest and hardiest of the herbs to grow from my experience, which also adds some nice bushiness AND a good pop of green to a maze of flowers? Summer Savory, bar none. While oregano and others die back in the winter, this li'l bush kept on keepin' on, giving a blessing of fresh herbs even during below-freezing temps...then came roaring back even more prolific this spring! The other great thing, of course, is it's an awesome flavoring for a multitude of dishes that need - get this - a pop of savory...