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Introduction

     The holiday cacti are epiphytic plants native to a small region in the Organ Mountains (22° south latitude) north of Rio de Janeiro, Brazil in South America. Rainfall varies from 17" per month in December to March to 3" per month in the dry season. Temperatures remain fairly constant at 60-70°F. Photoperiods range from 11 to 13½ hours. Schlumbergera truncata grows in the rain forest at an altitude between 3,000 and 5,000 feet, rooting into decaying organic debris trapped among tree branches or in rocky crevices on the ground in shady areas. Schlumbergera bridgesii grows at higher mountain altitudes in cooler, dryer wooded areas. Under natural conditions, Schlumbergera truncata will flower in mid to late November and Schlumbergera bridgesii in December, thus the common names 'Thanksgiving' and 'Christmas' cacti, respectively.

     Taxonomic confusion exists in older literature concerning the genus name and identification of the two species. Holiday cacti are now placed in the genus Schlumbergera but may appear as Zygocactus, Epiphyllum, Cereus, or Cactus. Schlumbergera truncata is the Thanksgiving Cactus, and Schlumbergera bridgesii is the Christmas Cactus. Most of the plants grown commercially and investigated in the literature are probably Thanksgiving Cactus. Both plants grow vegetatively by producing flat, leaf-like stem segments (phylloclades) connected at the mid-veins. The two species are similar except Schlumbergera truncata has 2-4 'saw-toothed' serrates along the phylloclade margins, cylindrical ovaries, and yellow anthers while Schlumbergera bridgesii has dentate margins, 4-5 angled ovaries, and purple anthers.

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Cultivars
     Considerable breeding has been undertaken in Europe and the United States resulting in a wide selection of flower colors including red, orange, magenta, lavender, and white. Other characteristics which vary among cultivars are branching density, uprightness, phylloclade shape, flower shape, and bloom time. Although flower color is the primary criterion which consumer evaluate, producers should evaluate performance, particularly the ability of specific cultivars to bloom in time for holiday sales. Many cultivars are the result of crosses between Schlumbergera truncata and Schlumbergera bridgesii.

Thanksgiving cactus cultivars
Christmas Charm Purple Red Radiance Blood Red Red Beauty Red
Christmas Magic Purple Twilight Tangerine Orange Sabrina Purple
Gold Charm Yellow White Christmas White Majestic Purple
Kris Kringle Wine Red Maria Carmine Christmas Cheer Brick Red
Lavender Doll Lavender Snowfire White Koeninger Brick Red
Peach Parfait Peach Sonja Rose Pink Norris Brick Red
Amethyst Rose Lavender Lady Rose Pink Margaret Carmine
Snow Flake White Weiss White    

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Photoperiod
     Holiday cacti are qualitative short-day plants for flowering and the photoperiodic response is modified by temperature (thermophotoperiodic). Plants grown at night temperatures between 50° and 59°F will flower regardless of photoperiod, however, development is slow and 50°F can cause flower bud abortion. Plants initiate flowers under short-days (8-10 hours) at 60° to 68° and remain vegetative under long-days. Flowering is delayed by night temperatures greater than of 68°F under short-days. To finish a crop under natural daylengths, flower initiation will occur about September 15. High temperatures in mid-September can delay induction.

     Schlumbergera truncata flowers about a month sooner than Schlumbergera bridgesii under natural daylengths. Plants require 4 or more phylloclades to be responsive to photoinductive treatment and individual phylloclades = 1 cm (about 20 days from emergence) will not initiate flowers. Plants require at least 20-25 days of continuous short-days (7 days a week) to initiate flowers, buds are microscopically visible in 12-14 days and visible to eye in 3-4 weeks. However, provide 6 weeks of short-days for complete bud set. Photoperiod has no effect on flower development once initiation has occurred. However, temperature can be raise or lowered to manipulate the speed of flower development once buds are visible (see scheduling). Total flowering time is 7-8 weeks at a 68°F night temperature and 9-10 weeks at 60°F. Two hours night interrupted lighting (11:00 pm - 1:00 am) at a 5-10 ft.ca. will inhibit flowering under photoinductive conditions. Night interrupted lighting is required from October 1 to March 1 to keep plants vegetative. Black cloth can be applied from 5:00 PM to 8:00 AM to induce flowers under noninductive photoperiods. Plants can be covered with black cloth from March 15 to September 15 to insure flower bud formation.

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Temperature
     Vegetative growth rate increases as average daily temperature increases from 50° to 77°F. Plants require about 60, 45, 38, or 28 days to development one phylloclade at 60, 65, 70, 75, or 80°F average daily temperature, respectively. Reasonable growing temperatures are probably 65-70°F nights and 75-80°F during the day, do not grow plants below 60°F night temperature.

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Light
     Plants can be grown in full light during the fall and winter but should be shaded during the summer. Recommended light intensities are 2,000-3,000 ft.ca. Marginal chlorosis is common on plants grown under high-light, high-temperature conditions in the summer.

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Growing Media
     Thanksgiving cactus are epiphytic plants that, in their native environment, root into decaying organic debris trapped among tree branches or in rocky crevices on the ground. Therefore, they require an exceptionally course, well drained medium with high porosity. Many growers use pure, course peat moss, though various ratios of peat (80-60%) and perlite (20-40%) work well. Coarse builders sand and styrofoam beads have also been used as media components. The media should have a pH of 5.5-6.2 and a low EC (0.5 mmhos/cm based on 2:1 extract). Trace elements can be added to the medium according to the product recommendations.

Soil tests sufficiency ranges for Holiday Cactus
Nutrient Range
Nitrate 25 - 60
Ammonium 0 - 25
Phosphorus 25 - 50
Potassium 75 - 175
Calcium 200 - 400
Magnesium 100 - 200

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Watering
     The media should be maintained evenly moist for maximum growth. However, they will not tolerate wet soil with low aeration. Subirrigation works well for Holiday cacti production. Water stress has no effect on flower induction and can cause delayed development, reduced flower size, and premature flower bud abscission. Water holiday cactus early in the day so the foliage will dry quickly, thus helping to prevent the likelihood of disease.

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Fertilization
     Target vegetative growth EC should be 0.7-1.0 mmhos/cm and pH 5.5-6.2 based on 2:1 extract. Growers should routinely monitor pH and soluble salts throughout the production cycle. Commercial fertilizers may be used at 150-200 ppm nitrogen including 20-10-20 or 15-16-17. These rates should be reduced by one-half for subirrigation. High ammonium fertilizer sources should be avoided in low light, low temperature conditions, especially when root rot diseases are a problem. Magnesium requirements are higher than in most plants and monthly application of Epsom salts (8 oz./100 gal.) can be given. Supplemental iron treatments (Sequestrene 330, 4-6 ounces / 100 gal.) may be needed several times during the growing season. Deficiency symptoms include marginal chlorosis and cupping of new segments, especially on 'Lavender Doll'. However, high iron and manganese can cause leaf scorch. Fertilization should reduced or stopped a month before the beginning of short days to increase the percentage of segments that produce flowers.

Tissue analysis sufficiency ranges Holiday Cactus
Macronutrients (%)
Micronutrients (ppm)
Nitrogen
2.10 - 6.00
Iron 50 - 225
Phosphorus
0.30 - 1.55
Manganese 27 - 200
Potassium
3.00 - 6.50
Boron 25 - 108
Calcium
1.00 - 2.00
Copper 6 - 38
Magnesium
0.35 - 0.85
Zinc 25 - 262
Sulphur
0.30 - 0.70
Molybdum No data

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Propagation
     Propagation is accomplished commercially by rooting mature single segment cuttings taken from stock plants or plants maintained vegetative from the previous crop. Segments may be stored for up to 6 weeks at 50-55°F and high relative humidity (90%). Segments are rooted in 72 or larger cell flats or in the final container and should be drenched with a broad-spectrum fungicide after sticking. Two or three cuttings may be stuck in a single flat cell. Night interrupted lighting is required from October 1 to March 1 to insure plants remain vegetative. Little (30 seconds per hour, 12 hours per day) or no mist is needed if watered adequately and if light intensity (1000-1500 ft.ca.) is controlled. Bottom heat applied at 70-77°F is beneficial during the winter months. The rooting medium is frequently the same one used for growing on. Fertilization can begin after rooting, about 2-3 weeks after sticking. Cutting are stuck from December through March depending on finishing date and final container size. Stock plants and cuttings should be maintained under long-days at all times.

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Potting
     The number of segments planted per pot varies with cultivar and pot size. The following are general guidelines: 2 or 3 inch pot - 1 segment, 3 inch pot - 2 segments, 4 or 4½ inch pot - 3-4 segments, and 5 or 6 inch pot - 4-6 segments. Many producers will transplant two or three established 4 inch pots into 8 or 10 inch hanging basket (results in 6-12 segments per pot).

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Pinching
     Plants are often pinched back to 2-3 segments when the terminal segments are 0.5-1.0 cm long in early June to increase branching and produce a fuller plant appearance. Increasing the temperature to 70-75°F for two weeks after the pinch will promote branching. Larger pot sizes may benefit from a second pinch. The segments removed can be rooted to establish stock plants for the following year. Typically, all pinching should be done by mid-June for flowering in late November to early December. Sanitary practices should be followed to prevent the pinching process from spreading diseases.

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Spacing
     Pot sizes 4½ inch or smaller can be grown pot-to-pot for all or most of the production period. Six inch pots require some additional space after about 14 weeks. Hanging baskets can be spaced on the bench or grown overhead on drip lines to maximize space utilization.

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Leveling
     Leveling (twisting) should maximize flower bud number and minimize vegetative growth. Phylloclades = 1 cm in length at the time short-days begins will not initiate flowers until they mature. These small segments (pads) should be removed 5-10 days after the beginning of short-days or they will produce unsightly additional vegetative segments. Additional shoot length can also be removed to shape the plant. Plants should be under short-days for at least 5 days before leveling. Segments > 1 cm will grow to mature size and initiated flower buds. Sanitary practices should be followed to prevent the leveling process from spreading diseases.

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Growth Regulator
     BA (6-benzyl-adenine) is a cytokinetin (growth regulator) that stimulates cell division. When applied to Holiday cactus at the time of floral initiation, BA results in an increase in the number of flower buds. Under non-photoinductive conditions, BA applications can increase branching after a pinch. Pro-Shear, one commercial BA formulation, should be applied as a spray 7-10 days after the beginning of short days (after leveling) at a rate of 8 ml / liter of water (100 ppm BA). Apply the spray to just short of run-off. It should be noted that response to BA applications varies with temperature and the cultivar. A second application may be needed a week later on some red cultivars. The following is a summary of steps to increase flower number: 1) level plants, 2) maintain short-days 7 days/week, 3) maintain night temperatures at 62-68°F, 4) apply BA 7-10 days after the start of short-days, 5) reduce nutrient levels prior to flower induction, and 6) avoid water stress during flower induction and development.

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Diseases


1. Fusarium oxysporum is often found in combination with fungus gnats causing major losses. Remove infected plants to prevent spread of the disease. Subirrigation reduces spread of the disease because splashing water from overhead watering carries the spores.

2. Phytophthora parasitica and Pythium aphanidermatum causes basal stem rot and root rot. Plants infected with Phytophthora parasitica appear wilted and dull gray-green with water-soaked necrotic areas near the soil line that are rather firm and faded reddish margins. Phylloclade abscission is common. Those infected with Pythium aphanidermatum have similar symptoms but without segment abscission and the reddish margins.

3. Rhizoctonia solani causes stem rot.

4. Erwinia carotovora subsp. carotovora causes blackish, wet, bacterial blight generally starting at the base of the plant and progressing throughout the stem. Remove infected plants and avoid splashing water.


Note: Use plastic gloves and dip in disinfectant solution to prevent the spread of disease, especially erwinia, during pinching and leveling.

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Insects

1. Caterpillars can become serious pest during certain times of the year by eating the segments.

2. Fungus gnat larvae can cause serious problems by eating the roots and segments close to the soil line, especially during propagation and when plants are young.

3. Mealybugs can become an impossible problem unless detected early and diligently eradicated.


Note: Diazinon applications to Holiday Cacti can cause severe stunting and distortion.

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Scheduling
     A temperature of 68°F should be maintained for maximum flower production from the beginning of short-days until buds are visible. Once buds are visible, the rate of flower development can be controlled using average daily temperature. Adjust temperatures based on the table below that shows the number of days to open flower for Thanksgiving Cactus based on temperature and initial flower bud length. The figure below show a 4-inch pot schedule.

Bud length (mm)
Days to flower
55°F 60°F 65°F 70°F 75°F
1
113 70 50 39 32
2
94 58 41 32 26
3
84 51 37 28 23
4
76 47 33 26 21
5
70 43 31 24 19
6
65 40 28 22 18
7
61 37 27 21 17
8
58 35 25 19 16
9
54 33 24 18 15
10
52 31 22 17 14
11
49 30 21 17 14
12
47 28 20 16 13
13
45 27 19 15 12
14
43 26 18 14 12
15
41 25 18 14 11
20
33 20 14 11 9
25
27 16 12 9 7
30
23 13 9 7 6
40
15 8 6 5 4
50
9 5 3 3 2
60
4 2 1 1 1

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