Agastache Mexican (Giant Hyssop) Lavender blue is a herbaceous perennial is best grown in moderately fertile, well drained soil which is kept on the dry side. It is both heat and drought tolerant and due to its aromatic properties is considered to be an excellent attractant to hummingbirds and butterflies. This species is also popular when used as dried flowers or as a cut flower.,Agastache Mexican (Giant Hyssop) Lavender blue is a herbaceous perennial is best grown in