Who does not know the lavender's perfume so characteristic of the Provence? The lavandin presents a better yield in essential oil that is used mainly in perfumes and cosmetics, but also in washing powders and cleaning materials. The chemical and thermal study, made on the same stalk of the lavandin, during the period from January to August, responds to two goals. First for economic appearance, we observed a higher yield of essential oil in open or wilted flowers. The automation of the flowers gathered has induced a decreasing of the essential oil in distillation, on account of the recovery of the branches without oil. Moreover, the water, mineral ashes, cellulose, lignin, holocellulose, and hemicellulose contents are computed in all the aerial parts (new and old leaves, branches). Second, the wild lavender, like other plants of the land of Provence, could be at the start of the forest fire. The inflammability risk can be observed by thermal analysis at about 300 degrees C: presence of an exothermic peak by DTA, weight loss by TG, and determination of the maximum decomposition rate by differential thermogravimetry (DTG). In high-heating rates (about 50 degrees C/min), the decomposition of the aerial parts of the plant increases mainly with the cellulose level.