Agastache 'Black Adder' | Giant hyssop
Smoky lilac-blue moody elegance
Grown by Mike's perennial specialists
UK
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Plant diary
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Agastache 'Black Adder'
Giant hyssop
- Add incredible, dark, moody sophistication to your planting scheme with the spectacular, smoky lilac-blue flowers emerging from striking, dark purple buds.
- Agastache 'Black Adder' creates a phenomenal, high-contrast display, bridging the gap beautifully between bright summer colors and rich autumnal tones.
- This agastache is exceptionally vigorous and reliable, rapidly forming a tall, sturdy clump that requires absolutely no messy, complicated staking.
- It boasts incredibly fragrant, minty-liquorice foliage that naturally deters pests while smelling absolutely divine when brushed past on a warm day.
- A total magnet for late-season butterflies and an outstanding, long-lasting cut flower, it is an indispensable workhorse for any vibrant, wildlife-friendly garden.
What to expect
Supplied as
Eventual height
Eventual spread
Flower colour
Habit
Hardiness
Will this grow in my garden?
Can I grow this in a pot?
Yes, Agastache 'Black Adder' grows well in pots with regular watering during dry spells.
How big does it get?
Agastache 'Black Adder' typically reaches a mature height of 90 cm and a spread of 50 cm.
How much sunlight does this need?
Agastache 'Black Adder' requires full sun for at least 6 hours a day.
What kind of soil does this plant prefer?
Agastache 'Black Adder' prefers well-drained, moderately fertile soil.
How much watering does this plant need?
Agastache 'Black Adder' is drought-tolerant once established, needing water only when the top 5 centimetres of soil feel dry.
Will this plant need pruning?
Agastache 'Black Adder' | Giant hyssop does not strictly need pruning, but regular deadheading will encourage more flowering. Cut the plant back to the base in late autumn or early spring.
How hardy is this plant?
Agastache 'Black Adder' is rated H3 or H4, tolerating temperatures down to -5°C to -10°C. It may survive winters in mild southern UK gardens with good drainage, but often requires protection in colder northern areas.
The wider garden
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