It’s a lot of trouble to get this year’s poinsettias to bloom
again next year, but the result can be worth it.

Poinsettias originate from Mexico, where they bloom during the
winter. They prefer bright, sunny windows and evenly moist
conditions. But for the colorful bracts to develop, they have to
have nights longer than 12 hours.

They begin to set buds and produce flowers as the nights become
longer than days. In Georgia, this happens around Sept. 25. If
you don’t provide artificially long “nights,” poinsettias will
stay green all winter.

Trigger New Bracts

To trigger new bracts, bring poinsettias indoors in early October
and place them in a sunny window. Continue to grow them as you
did outdoors, except with less fertilizer.

Beginning that week, keep the plant in complete darkness for 14
continuous hours each night by moving plants into a dark room or
placing a large box over them.

If light reaches the plant accidentally during this period, it
may revert to its vegetative state and stay green. During the
day, allow 6 to 8 hours of bright sunlight. Keep this up for
eight to 10 weeks, or until about Nov. 15.