• Agastache &
  • Agastache &
  • Agastache &
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Agastache 'Blackadder'

Giant Hyssop, Anise Hyssop

£6.99
£6.99
Agastache 'Blackadder' is a stunning perennial that produces dense spikes of deep violet-blue flowers from mid-summer to autumn, bringing vibrant colour and a magnet for bees and butterflies.
  • Long-lasting flowers from summer to autumn
  • Attracts bees, butterflies, and other pollinators
  • Aromatic, licorice-scented foliage
  • Drought-tolerant and low-maintenance
Size

    • Aspect

      Full sun

    • Hardiness

      Hardy

    • Flowers

      July, August, September, October

    • Soil type

      Well-drained, Loamy, Sandy

    Agastache &
    Agastache &
    Agastache &

    • Why we like this plant

      Agastache 'Blackadder' is an excellent choice for gardeners seeking a long-flowering, pollinator-friendly perennial that thrives in sunny and well-drained conditions. Its deep blue flower spikes add height and movement to borders, while its aromatic foliage provides an additional sensory element. Perfect for wildlife gardens, prairie planting schemes, or mixed perennial beds, this hardy and resilient plant delivers beauty and ecological benefits in equal measure.

    • About this plant

      Agastache 'Blackadder', commonly known as Giant Hyssop or Anise Hyssop, is a standout herbaceous perennial loved for its long-lasting floral display and aromatic foliage. Its tall, upright stems are adorned with spires of deep blue-purple flowers, which appear from mid to late summer, creating a dramatic vertical accent in borders and wildlife-friendly gardens. The dark green, anise-scented leaves add further sensory appeal, releasing a delightful fragrance when brushed against. This hardy and drought-tolerant plant thrives in well-drained soil and full sun, making it an excellent choice for dry, sunny borders, prairie-style plantings, and container displays.

    • Key features

      • Elegant spikes of deep blue-purple flowers
      • Attracts bees, butterflies, and other pollinators
      • Aromatic, anise-scented foliage
      • Drought-tolerant once established
      • Ideal for sunny borders and wildlife gardens

    • Height and
      spread

    • Growth
      habit

      Upright, clump-forming

    • Moisture

      Moderate; drought-tolerant once established

    • Position in
      the Garden

      Sunny borders, wildlife gardens, prairie-style planting, containers

    Planting guide

    • Plant in a sunny position with well-drained soil
    • Space plants approximately 30–45cm apart
    • Improve heavy clay soils with grit or compost to enhance drainage

    Care tips

    • Plant in well-drained soil in full sun
    • Deadhead spent flowers to encourage continuous blooming
    • Cut back stems in late autumn or early spring for new growth
    • Water moderately until established, then drought-tolerant
    • Apply mulch in spring to retain moisture and suppress weeds

    Winter care

    • Leave faded flower spikes for winter interest and wildlife benefit
    • Apply a light mulch in colder regions for added protection
    • Cut back in early spring to encourage fresh growth