Botanical Name: Agastache ‘Black Adder’

Common Name: Hummingbird Mint, Anise Hyssop Hybrid

Hardiness Zone: Perennial in Most Climates (USDA Zones 6–10)

Size: 30–36" Tall × 18–24" Spread

Growth Habit: Upright, Clump-Forming Habit

Sunlight: Thrives in Full Sun

Soil: Prefers Well-Drained Soil; Tolerates Poor or Rocky Soils

Water Needs: Low to Moderate Once Established; Drought Tolerant

Bloom Season: Early Summer through Fall

Fertilizer: Light Feeding in Spring; Avoid Excess Nitrogen

Features: Deep Blue-Purple Flower Spikes, Dark Calyxes, Aromatic Foliage, Deer Resistant, Exceptional Pollinator Plant

Uses: Ideal for Pollinator Gardens, Perennial Borders, Cottage Gardens, and Naturalistic Plantings

Patent: ❌ Not Patented

Propagation: ✔ Propagation Allowed

See our complete Agastache Growth & Care Guide for full care details.

More About Agastache ‘Black Adder’

Agastache ‘Black Adder’ is one of the most iconic hummingbird mints ever introduced, valued for its dramatic contrast between deep violet-blue flower spikes and nearly black calyxes. This dark coloration gives the plant a bold, architectural presence that stands out from a distance and adds depth to mixed perennial plantings.

Originally bred as a hybrid between Agastache foeniculum and Agastache rugosa, ‘Black Adder’ combines the cold tolerance and fragrance of anise hyssop with improved flower size and garden performance. The upright flower spikes are densely packed and long-lasting, creating continuous vertical interest from early summer well into fall.

Why We Like It (Our Trials)

In our trials, ‘Black Adder’ has proven to be a dependable, high-impact perennial with outstanding pollinator activity. Bees, butterflies, and hummingbirds visit constantly, making it one of the most reliable nectar plants for wildlife-focused gardens. Once established, it handles heat and drought with ease, provided the soil drains well.

We also appreciate its natural, slightly looser habit compared to more modern compact Agastache varieties. It excels in larger borders, meadow-style plantings, and pollinator gardens where height and movement are desirable. Deer consistently avoid it, and the aromatic foliage helps reduce pressure from browsing animals.

Agastache ‘Black Adder’ vs. Newer Agastache Varieties

Agastache ‘Black Adder’ is often considered the benchmark for tall, dramatic Agastache, valued for its strong vertical presence and deep, saturated violet-purple flower spikes. Compared to more compact selections like ‘Little Adder’, Black Adder grows taller and airier, making it better suited for mid- to back-of-border placements where height and movement are desirable. While it lacks the tight, mounded control of dwarf types, its upright stems and long bloom season give it a bold, architectural quality that performs exceptionally well in naturalistic and pollinator-focused landscapes.

When contrasted with modern, densely flowered varieties such as ‘Blue Boa’, Black Adder appears more open and meadow-like, offering a lighter, less congested silhouette. ‘Blue Fortune’ shares a similar airy character but with a softer blue tone, but Black Adder delivers deeper color and stronger contrast when paired with warm hues like ‘Kudos® Mandarin’ or ‘Kudos® Coral’. For gardeners who prioritize height, hummingbird attraction, and a more traditional prairie aesthetic, ‘Black Adder’ remains one of the most impactful and time-tested Agastache selections available.