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: average
• Flowering period: July to September
• Hardiness: frost hardy (may need winter protection)
  
  This towering beauty produces its clear blue flowers over a couple of months from midsummer - so it's perfect for adding soft, unstructured height and colour to the back of the border. As its common name suggests, it is happiest in soils that are reliably moist but not waterlogged, and it prefers a sunny spot. The flowers mix well with most pinks, purples and plums, and they are also sought after by bees and butterflies.
  
  
• 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 spring.