• True lilies require cold weather to rest after each growing season.pink lilies image by leafy from Fotolia.com
  
  

Some Lilies Are Not Hardy

• Some plants are called lilies simply because of their flowers.Calla in fiore image by Gionata_d from Fotolia.com
  
  Denver gardeners should lift calla, cannas and water lilies from the ground in the fall because they are tender tropical tubers.
  
  

True Lilies Require Cold

• Hardy Asiatic hybrids need not be mulched in Denver's mild winters.Lilies image by TC from Fotolia.com
  
  True lilies require a period of cold rest called dormancy after blooming. Denver's mild, semi-arid climate resembles many lilies' native habitats.
  
  

Bottom Line

• Martagon and other species are hardy in Denver.lily martagon image by hazel proudlove from Fotolia.com
  
  Don't lift true lily bulbs in Denver gardens for the winter, but provide them with extra moisture throughout the summer when the air is dry.