During a party an entire stem of a poinsettia complete with several leaves ended up being snapped off the main plant. I put it in some water and put it in a temperate and indirect light part of the house but haven't done anything with it since. To my amazement even though the main plant appears to be going dormant and shedding its leaves, this broken stem is growing new leaves and retaining all its existing red ones (though some green ones fell off). It doesn't appear to have put any roots out and I haven't done anything other than top the water up. Is there anything I can do to encourage it to root?