Yarrow, or Achillea as it is known botanically, can be grown for the flower or as an herb. Yarrow seeds can be direct sown in spring or started indoors. It is an easy care perennial that thrives in full sun and is not fussy about soil conditions. Achillea has been used for centuries as a medicinal herb and it acts as a lure for beneficial insects. The astringent qualities of yarrow are said to be useful in fighting cold and flu. All around, this tall, decorative plant is one of the most highly prized companion plants and lure for beneficial garden insects.