Do poinsettias need artificial darkness

For about ten (10) weeks after a start date anytime between September 20 and October 20 poinsettias (Euphorbia pulcherrima) need artificial darkness.

Specifically, that start date is the time at which poinsettias naturally initiate the process that culminates in the plant's late December bloom. In order for the process to start, poinsettias need no less than 12 hours 20 minutes of darkness on a daily basis during the above-mentioned time period. But in actuality the flowering process is jump-started anytime during the year in which the previously listed conditions are met. It therefore is possible to see the dainty, inconspicuous yellow flowers and the brightly colored modified leaves at times other than the end of the year.