Hardy and reliable, Agastache 'Black Adder' (Giant Hyssop) is a charming herbaceous perennial boasting bottle-brush, terminal spikes, 6-8 in. long (15-20 cm), packed with fragrant, tubular, two-lipped red-violet flowers emerging from dark buds. Blooming from mid-summer to fall, they provide a remarkably long floral display and add color as well as a lovely spiky texture to the garden.

• Forms upright clumps up to 2-3 feet tall (60-90 cm) and 18-24 in. wide (45-60 cm), with aromatic, blue-green leaves which exude an anise scent when crushed.
• Provides a bold visual impact in beds and borders, cottage gardens, gravel gardens, butterfly gardens, or Mediterranean gardens over a very long season.
• Ideal to add color to the late-season garden when many other plants are fading.
• Creates a stunning effect when mixed with other perennials or planted en masse.
• Attracts streams of hummingbirds, butterflies, and other beneficial pollinators.
• Easily grown in full sun, in average, dry to medium moisture, well-drained soils. Good drainage is particularly important.
• Drought, dry soil, and heat tolerant once established.
• Generally disease and pest-free (might occasionally be subject to powdery mildew) and resistant to deer and rabbits.
• Trim back stems in late autumn to reduce windrock. Prune flowered stems back in spring.
• Root semi-ripe cuttings in late summer and overwinter under cover; propagate by division in spring. This cultivar is sterile.