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CommentsThe pale yellow flowers are not very showy because they seem small in comparison to the rest of the plant and only a few flowers are in bloom at the same time. Thus, the attractiveness of Yellow Giant Hyssop consists primarily of its foliage. Other species in this genus that occur in Illinois are Agastache scrophulariaefolia (Blue Giant Hyssop) and Agastache foeniculum (Anise Hyssop). Blue Giant Hyssop is about the same size as Yellow Giant Hyssop and it has a similar appearance, except that the corolla of its flowers are blue and its stems are pubescent. Anise Hyssop has a shorter stature than the preceding species and its foliage has an anise scent; it also has flowers with blue corollas.