L. angustifolia is the one to use for culinary purposes: Two most popular varieties are Munstead or Hidcote. They are referred to as 'sweet lavender'.
The intermedias-lavandins- and dentata are best for fragrance and craft use. Lavandins have the longest stems and color holds well.
Don't fertilize - overdoing causes loss of scent and affects oil quality. Could spread some compost around plant in early spring