Winterberry plants (Ilex verticillata) are best propagated through softwood cuttings taken in late spring or early summer, treated with rooting hormone, and rooted under mist or in a humid environment

Here’s a more detailed guide:

1. Timing and Plant Selection:

  • Best Time: Late spring to midsummer is ideal for taking softwood cuttings. 
  • Plant Selection: Choose cuttings from a mature, female winterberry plant that has produced berries for at least a season. 
  • Suckers: Winterberry plants can also spread by suckers (new shoots from the roots), which can be dug up and replanted. 

2. Taking Cuttings:

  • Stem Selection: Select 2-3 inch stem tips from new growth.
  • Cutting: Use clean sheers or pruners to trim the stem tips.
  • Leaf Removal: Remove all but the top pair of leaves on each stem.
  • Rooting Hormone: Dip the cut end of the stem into rooting hormone.