PLANT OF THE WEEK

Dr. T. Ombrello - UCC Biology Department

HOLIDAY CACTI

Common names:  

1. Christmas Cactus
2. Thanksgiving Cactus ( Crab Cactus, Claw Cactus, Yoke Cactus, Linkleaf Cactus)  
3. Easter Cactus

Scientific  names:       

1. Schlumbergera Bridgesii

2. Schlumbergera truncata (formerly Zygocactus truncatus)

3. Schlumbergera Gaertneri (formerly Rhipsalidopsis Gaertneri)

Explanation of scientific names:       

Schlumbergera        - named for Frederick Schlumberger, a student of plants

 
Bridgesii                    - named for R. Bridges

truncata                    - truncate, cut off square, in reference to the ends of the stems

Gaertneri                   - named for E. Gaertner

While most people consider all of the holiday flowering cacti to be the Christmas Cactus, there are really 3 different species (Christmas Cactus, Thanksgiving Cactus and Easter Cactus) that are sold in the horticultural trade. At first glance they all look essentially the same, and this should come as no surprise since many of the cultivated forms have been produced through hybridization among the different species of Schlumbergera and with the related genera Epiphyllum and Cereus. Our manipulation of these plants has been so complete that typical, natural specimens are rarely seen. As a result, the scientific classification of these cacti has been and still is confusing with no complete agreement among plant taxonomists.

The 3 species, while similar in appearance, have different times of bloom, so it is important to be able to differentiate amongst them if one would like to know when to expect flowers. Unfortunately, all 3 species are often incorrectly labeled as Christmas Cacti in florists and garden centers. The following are brief descriptions of the 3 species, emphasizing the major differences amongst them.

Christmas Cactus   The stem segments are not toothed, but instead gently scalloped along the edges. The flowers are generally carmine red, tinged purple in the center, and perfectly symmetrical. They bloom any time from December to February.

Thanksgiving Cactus   This species is sometimes called the Crab Cactus because the stem segments have prominent pointed teeth, giving them the appearance of crab claws. The basic flower color is scarlet, but hybridizers have produced varieties with colors ranging from orange, yellow, peach, lavender and purple, to white. The flowers are all symmetrically irregular (zygomorphic), and hence the former genus name Zygocactus. The flowers appear in late October and continue through November. In some, a second bloom period begins in late winter. This species is the one most commonly sold in our area in the fall and winter.

Easter Cactus    This species is very similar in appearance to the Christmas Cactus, but is generally more compact with the stem segments having short bristles growing from their edges. Its regular, star-like flowers are pink to dark scarlet in color and bloom in March or April.

Native to the tropical mountainous regions of South America (especially Brazil) these true cacti are quite different from what most people think of as cacti growing in a desert. These tropical cacti are epiphytic in that they do not grow on the ground, but instead grow in the crotches of tree limbs on debris and decaying organic matter. Along with other tropical cacti they are ancient relics that seem to have been left behind as their ancestors advanced and adapted to drier and more exposed habitats. The holiday cacti remain as “living fossils”, suggesting an evolutionary link with the past.

In nature the holiday cacti grow rapidly during the rainy season, and are dormant during the dry season. They survive drought by utilizing moisture stored in the flattened, jointed stem segments that also serve as the photosynthetic organs since the plants do not develop leaves. In contrast to most cacti, the holiday cacti are not well armed. Their spines are minute or non-existent. The stems grow upright for a while, but eventually branch and bend downwards, giving the plant a pendulous appearance. All 3 species are long-lived and, with age, form mounds of arching, linked segments. Since they are vigorous, sturdy, and tolerant of neglect, plants can develop into magnificent specimens and sometimes become heirlooms within a family.

When grown in the home, the holiday cacti thrive best if the environmental conditions mimic what they would experience in nature. The plants need bright light, but not necessarily full sun. This is what they would experience growing high in the branches of trees. When actively growing and especially when buds are developing or the flowers are open, the soil should be kept moist with just a slight amount of drying between waterings, as would occur during their rainy season back home. After the blooms fade, the plants should be kept on the dry side. The soil in which they grow as houseplants should be well drained, rich in organic matter, but not necessarily sandy. They are not your typical desert cacti! The plants will do well outdoors during the summer, but are intolerant of late spring or early fall frosts.

Flower initiation on the holiday cacti depends on temperature and sometimes daylength. The following relationships have been worked out: