If your poinsettias spent the summer outdoors, they should be back indoors by late September or early October. Sensitive to day length, the poinsettia needs a certain minimum amount of darkness each 24-hour period to stimulate blooming in the winter. With the shorter fall and winter days in Oregon, the poinsettia has a natural tendency to want to bloom in the fall, when there are about equal amounts of dark and light. Start in late October or early November.
People often forget to cover the plant one or two nights.
Interrupting the darkness by even a few minutes may cause failure of bloom. Bring the plant to ordinary light after the bracts show color. Poinsettia growers may have better luck if the bracts are almost fully expanded before bringing the plant out. Once the plant has large, colored bracts, the artificial light inside a house will not inhibit a poinsettia's blooms. Early December - Bract color should be almost complete.