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

• Position: full sun
• Soil: moderately fertile, moist but well-drained soil
• Rate of growth: fast
• Flowering period: August to October
• Hardiness: half hardy (will need winter protection)
  
  This head-turning perennial offers both stature and sumptuous colour. It's an impressive sight in late summer and autumn when the dark, 30cm long spikes appear, each threaded with rich purple-blue flowers that are held at their bases by near-black calyces. 'Black and Blue' is a vigorous plant, but it's not fully hardy, so if possible place it near a south facing wall where it will flourish in its reflected warmth and shelter.
  
  
• Garden care: To prolong flowering remove the flower spikes as soon as they start to fade. Apply a generous 5-7cm (2-3in) mulch of well-rotted garden compost or manure around the base of the plant in autumn to help insulate the roots throughout winter. Also, resist cutting back the top growth in autumn, as this will also help protect the plant against frosts. Instead, cut them back in late spring when the fresh new growth is starting to emerge.