This perennial dies back to below ground level each year in autumn, then fresh new growth appears again in spring.

• Position: full sun
• Soil: well-drained, fertile soil
• Rate of growth: average
• Flowering period: July to October
• Hardiness: fully hardy (borderline)
  
  Hyssops are great for adding height to a border, with whorls of long-lasting, tiny flowers arranged like a bottlebrush, and pointed, aromatic fresh green leaves that are attractive to butterflies. They are short-lived though, and may need replacing every few years, especially after a cold or wet winter. 'Blackadder' has smoky, violet flowers on long spires from July to October. Try it as part of a Mediterranean scheme or in a sunny, well-drained border among ornamental grasses.
  
  
• Garden care: Don't cut back the faded flower-stems until early spring, as they provide interest in the winter months. Lift and divide congested colonies in spring.