Holiday cacti, commonly called Christmas cacti, Thanksgiving cacti, or Zygocactus, are one the most popular flowering plants at this time of year. The "real" Christmas cactus is an interspecific hybrid of Schlumbergera truncata and Schlumbergera russelliana. Its correct Latin name is Schlumbergera xbuckleyi. This hybrid originated in England about 150 years ago. Christmas cacti have segments with rounded margins, flowers have ribbed ovaries and purplish-brown anthers. Most commercial cultivars of holiday cacti are really Schlumbergera truncata. These cultivars are commonly known as Thanksgiving cacti or Zygocactus. The Thanksgiving cactus has segments with conspicuous teeth on the margins, flowers have rounded ovaries with no ribs and yellow anthers. Some cultivars of holiday cacti are derived from crossing the Christmas cactus and Thanksgiving cactus. These plants have characteristics of both parents.
Numerous cultivars of holiday cacti are grown. They differ in branching habit, rate of growth, shape of foliage segments and flowers, flower color, time of flowering, and plant habit (pendulous, semi-pendulous, or erect). Consumers buy plants based primarily on flower color and number. Flowering of holiday cacti is controlled by photoperiod and temperature. When temperatures are between 50 and 59 F, flower initiation occurs under any photoperiod including continuous lighting. When temperatures are between 60 and 75 F, plants initiate flowers under short days but remain vegetative under long days. The critical daylength is between 12 1/2 and 14 hours. Plants initiate flower buds when the days become shorter than the critical daylength which occurs naturally in the fall of the year. That's why holiday cacti are one of the easier plants for homeowners to get to flower. Holiday cacti often bloom much earlier than Christmas. To prevent this, provide your plants with more than 12 hours of light a day until mid October. After mid October, give your plants 14 to 16 hours of continuous darkness each day for at least 3 weeks. Your plants should start to bloom at Christmas.
A study done at the University of Massachusetts in 1991 comparing several varieties showed some top holiday cactus performers. 'Eva' has the traditional Thanksgiving cactus appearance with prominent teeth or points along the foliage segments. The plant has a semi-pendulous growth habit with magenta purple flowers. 'Linda' also has a semi-pendulous habit and prominent teeth; however, it has red flowers. 'Madisto' has an upright form with prominent teeth and light lavender flowers. 'Yantra' has an upright growth habit, prominent teeth along the foliage segments, and magenta purple flowers. 'Zarailca' has prominent teeth, an upright form, and crimson red flowers. Other recommended varieties include 'Christmas Charm' with magenta purple flowers. This plant has an upright habit and small teeth along the foliage edges. 'Madonga' also has an upright habit, small teeth, and magenta purple flowers. 'Marie' and 'Thor- Alise' have scarlet red flowers, large teeth, and a semi- pendulous form. 'Gina' and 'Thor-Britta' have white flowers, large teeth, and a semi-pendulous growth habit. 'Christmas Fantasy' has peach colored blossoms, 'Christmas Flame' has golden yellow flowers, 'Gold Charm' has pale yellow flowers, and 'Twilight Tangerine' has deep orange flowers. All four have prominent teeth along the foliage and an upright growth habit. 'Illona' has salmon orange flowers with a semi-pendulous habit. It also has prominent teeth.
A wide selection of holiday cacti are available at this time of year. They are an easy care houseplant for your own enjoyment or for holiday gift giving. They are more carefree than the traditional poinsettia and more rewarding when it comes to reflowering.
This article originally appeared in the December 9, 1994 issue, p. 162.