Lavenders are usually grown for the essential oil which for highest quality, as used in perfumery and cosmetics, is extracted from the buds and flowers. The leaf hairs also have some of these essential oils and may be used for sachets (often with flowers) or as a slightly sweet, floral flavor in cooking.
I’m afraid I grow them primarily for the shape, texture and color of the leaves, as in this climate I am lucky to see more than a few buds by first frost. As of late June ‘Goodwin’ is the only cultivar with a trace of buds.
I buy them in 3” pots and transplant them into a raised bed—they like it hot and dry, which does not exactly describe Interior Alaska in summer, even in Fairbanks. But they have a nice variety of appearances.