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Yellow giant hyssop plants are 4-7' tall; the stems are square and conspicuously winged. Flower spikes are up to 8" long. The calyx of the flowers is tubular and green in color; the corolla is ~3/8" long, nominally yellow, with an upper and lower lip between which protrude 4 stamens with yellow anthers and a style with a cleft tip. When in bloom, yellow giant hyssop is easily distinguished from other giant hyssops by the yellow/cream flowers.

Agastache

Agastache nepetoides

yellow giant hyssop [Blooms: Jul-?]