Agastache 'Black Adder'

Agastache 'Black Adder': Bold Spikes and Pollinator Magnetism

Agastache 'Black Adder' makes a striking impression in the summer garden with its dramatic violet-blue flower spikes rising from smoky, near-black buds. Flowering steadily from midsummer into fall, this tall, upright perennial brings strong vertical interest, bold colour contrast, and exceptional pollinator value to full-sun landscapes. Aromatic, licorice-scented foliage adds texture and sensory appeal, while its drought tolerance and deer resistance make it a tough, low-maintenance choice. Whether in a prairie-style border or a pollinator garden, 'Black Adder' delivers powerful performance and undeniable flair.

Plant Characteristics:

• Height: 90–120 cm
• Spread: 45–60 cm, forming a well-behaved upright clump
• Flower Colour: Violet-blue blooms emerging from dark purple-black buds
• Flowering Period: Midsummer to early fall
• Foliage: Green, toothed foliage with a sweet anise scent
• Sunlight Requirements: Full sun (minimum 6 hours of direct light)
• Soil Requirements: Well-drained soil; thrives in sandy or gravelly conditions

Uses and Benefits: 'Black Adder' excels in sunny, dry gardens where its deep-coloured spikes stand out among lighter perennials and ornamental grasses. Highly attractive to bees, butterflies, and hummingbirds, it offers continuous bloom and structural interest through the hottest months. Its upright habit makes it an excellent background or focal plant in mixed borders, and it’s equally useful in cutting gardens for fresh or dried arrangements. Deer resistance and low water needs ensure reliable performance with minimal care.

Companion Plants: Pair 'Black Adder' with Echinacea purpurea 'Magnus' for a bold pairing of colour and form, each attracting a parade of pollinators. Add Achillea 'Sassy Summer Sangria' for warm red umbels that contrast beautifully with the cool tones of the agastache. Complete the combination with Pennisetum alopecuroides 'Hameln'—its soft, arching plumes and fine blades offer movement and balance the vertical spikes with late-season elegance.

Care Instructions: Water regularly during the first season. Once established, 'Black Adder' is drought tolerant and thrives with minimal input. Deadhead to encourage repeat flowering and prevent self-seeding. Cut back to the base in late fall or early spring. Avoid overly rich or wet soils to maintain strong, upright growth.

History: A hybrid of Agastache rugosa and Agastache foeniculum, 'Black Adder' was bred for ornamental value, vigour, and a longer flowering window. Combining the best traits of its parent species—aromatic foliage, upright structure, and dense flower spikes—it has become a staple for pollinator-focused and drought-tolerant plantings. Its dramatic buds and dark colour set it apart from more pastel-toned cultivars, making it a favourite among contemporary garden designers.

Final Thoughts: With its bold flower spikes, fragrant foliage, and unwavering pollinator appeal, Agastache 'Black Adder' is a standout in any sunny, low-maintenance planting. It adds depth, movement, and long-lasting colour to borders while supporting biodiversity from midsummer into fall. Rugged yet refined, this perennial earns its place in modern and classic gardens alike.