Three different species of chamomile-German chamomile, Roman chamomile and chamomile mixta-are cultivated for their essential oils. All are members of the Asteraceae family and share similar properties.

The fine feathery leaves of the Roman chamomile plant (Chamamelum nobile or Anthemis nobilis) surround tiny daisylike flowers that are white with bright yellow centers. This perennial plant attains a height of nine to twelve inches. Native to southern and western Europe, Roman chamomile is now cultivated in many different countries, including Belgium, Bulgaria, England, France, Hungary and Italy. Steam distillation of the flowers renders a yellow essential oil with a sweet, warm herbaceous odor.

German chamomile (Matricaria chamomilla or Matricaria recutita) is similar in appearance to Roman chamomile, except that it is taller (it grows about two feet tall) and its flowers have smaller heads and fewer petals. German chamomile is an annual. Once native to Europe and parts of Asia, it now grows in Eastern Europe, Egypt, North America and in areas of the former Soviet Union. German chamomile oil has a characteristic deep blue or bluish green color, and for this reason is sometimes referred to as blue chamomile. It gets its color from its high content of azulene, a chemical component that is produced during the distillation process and that also has a strong anti-inflammatory action. Stronger in smell than Roman chamomile oil, German chamomile oil has a sweet, slightly fruity, slightly spicy scent that is almost intoxicating.