At its best:
Jun, Jul, Aug
Lily of the valley crowns are available in garden centres or online, at around £4 for 15. They’re hard to establish in cold, wet soil outside, so plant in pots first.
Soak roots in water for half an hour if they look dry. Carefully separate into individual crowns, each with a shoot and set of roots. Plant one per 7-8cm pot.
Fill the pot with compost, leaving the shoot just above the surface. Water, then place in a cool greenhouse. Keep watering and plant out once the roots fill the pot.