We are all trying to find some peace and pleasure at the end of this tumultuous, frustrating, and frightening year. If you are like me, you want to brighten up your house and spirits during the dark, cold days of winter. Exotic houseplants like Christmas cactus and poinsettia will bring cheerful color to your home.

Christmas cactus (Schlumbergera bridgesii) and its relatives, Thanksgiving cactus (Schlumbergera truncata) and Easter cactus (Rhipsalidopsis gaertneri) are perennial holiday favorites. These cacti lack true leaves; the stem segments are called phylloclades, and they differ between species. Christmas cactus stem segments are rounded, while those on Thanksgiving cactus are serrated. Easter cactus has pointed teeth and fibrous hairs in the segment joints and blooms in the spring. Identification is important so you won’t be disappointed when your cactus doesn’t bloom during the expected season.

Light and temperature are the two most significant factors affecting bloom. Du...