There are 28 species of lavender, but since they have been cultivated for centuries and tend to interbreed easily, there tends to be some disagreement as to proper names. The best time to harvest the flowers is when they are newly opened. At this point they can be used fresh, or cut long stems to dry for later use. Not only visually pleasing, they perfume the room they are in. When the fragrance begins to fade, just squeeze the blossom end to release the aroma.
Lavender is ideal for dried arrangements, and lasts quite a long time.
The blossoms retain their color and fragrance long after the stems have turned brown. As with the wands, crushing the blossoms releases the oils, reviving the scent. While thought of primarily for its fragrance, lavender does play an important, if some what subtle role in cooking. Generally it is the flowers that are used although sometimes the leaves are used in recipes from southern France. They reportedly have a slightly bitter taste.