Agastache 'Blackadder'
"Giant hyssop"
Orders placed before 1 March 2025
You can expect your order in February/March 2025
Orders placed 1 March - 15 April 2025
You can expect your order in March/April 2025
Orders placed 16 April - 15 May 2025
You can expect your order within 10 business days
UK orders over £50
Free shipping
UK orders under £50
£4.99
Northern Ireland orders under £50
£5.99
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Description
Introduce long-lasting colour, structural interest and a subtle aniseed aroma to your garden with impressive Agastache 'Blackadder'. Not only does this bushy giant hyssop pad out a patch with very attractive flowers during summer and autumn, but it will also be a welcome pit-stop for bees, butterflies and other pollinators. Upright flower spikes in an eye-catching shade of deep purple-blue are dotted with masses of small lilac-coloured flowers which gives the blooms an overall purple haze appearance, while the leaves emit a fresh, spicy fragrance.
Agastache 'Blackadder' tolerates heat and drought well, thriving in a free-draining soil. Its tolerance to what can be harsh summer conditions makes this an undemanding and reliable choice for the border. This giant hyssop is quite hardy, tolerating winter temperatures down to around -10°C in a sunny, sheltered position with free-draining soil. In areas with fairly mild winters, Agastache 'Blackadder' will grow back bigger and bushier each year!
Traditionally, Agastache was utilized for its medicinal qualities, thanks to its essential oils that would hold antimicrobial, anti-inflammatory, and digestive attributes.
Key features
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Perfect for pots
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Comes back every year
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Fragrant
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Attractive to wildlife
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Loved by pollinators
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Thrives well in full sun
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In peat-free compost
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Low maintenance
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RHS Award (AGM)
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Drought tolerant
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Fully hardy
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Rodent resistant
Specs & details
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Botanical name
Agastache 'Blackadder' syn. Agastache 'Black Adder'
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Flower colour
Purple, blue, near-black
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Plant size
1
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Established height
70cm-1m
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Established spread
20-30cm
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Plant spacing
6 plants per m2
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Leaf colour
Green
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Habit
Clump-forming
Upright -
Life cycle
Short-lived perennial
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Hardiness
Fully hardy
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Years to establish
1-2 years
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Sunlight
Full sun
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Position
Sheltered
Exposed -
Suitable for
Pots
Large containers
Borders
Gravel gardens
Wildlife gardens
Cottage gardens
Low maintenance gardens -
Soil acidity
Any
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Soil moisture
Free draining
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Soil type
Clay
Multipurpose compost -
RHS Award (AGM)
Yes
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Growing skill
Easy to grow
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Scented
Yes
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Pollinator-friendly
Yes
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Mouse resistant
Yes
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Rabbit resistant
Yes
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Deer resistant
Yes
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Toxicity
No report
Plant calendar
| Jan | Feb | Mar | Apr | May | June | July | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
- Planting
- Flowering
Useful information
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Soak your Agastache 'Blackadder' roots in water for 3-6 hours prior to planting.
Plant your "Giant hyssop" bare roots into temporary pots with a multipurpose compost in spring and grow-on in a sheltered spot outdoors.
Choose a pot which comfortably fits the bare roots. Some have a noticeable crown which should be just below the soil surface with any top growth exposed.
Plant out into borders or permanent containers in late spring or early summer once in full growth. Choose a position in sun or shade depending on the variety.
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Orders placed before 1 March 2025
You can expect your order in Feb/March 2025Orders placed 1 March - 15 April 2025
You can expect your order in April 2025Orders placed 16 April - 15 May 2025
You can expect your order within 10 business days
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