Few people think of cacti living in some of the most humid conditions imaginable, but the very popular holiday flowering cacti (Thanksgiving, Christmas and Easter cactus) are all in this group.

Their appearance is very different from dry land cacti. Most have wide, flattened, green stems that look much like leaves, no thorns and are grown primarily for their profuse and colorful flowers. They are popular gift plants.

CULTURE OF RAIN FOREST CACTI

Holiday cacti and other rain forest cacti need substantially more water, but should never be waterlogged. Never let them dry out completely during the spring and summer months. They prefer at least 50 percent humidity, but will tolerate less. Misting may be beneficial in the home.

These cacti need bright but filtered light. They may sunburn if in direct sun.

Rain forest type cacti require more organic matter in their soil mix than do desert type cacti. A good soil mix consists of two parts peat moss, one part garden soil and one part sand. Good drainage is essential.

Fertilize your plants once a month during the growing season with a well-balanced liquid fertilizer. Stop fertilizing Thanksgiving and Christmas cacti in September. Resume fertilizing after flowering. Easter cacti can be fed all year long except when flowering.

You can encourage flowering in holiday cacti by adjusting their nighttime temperature and the amount of light and water that they receive. If you grow these cacti under artificial light, make sure that they are in darkness for at least 12 hours each day during the fall. Holiday cacti need long nights to flower. Watering should be reduced about the end of September. This is a rest period for the plant and is necessary to set buds. Keep nighttime temperatures around 50 to 55 °F. Temperatures above this range may result in growth but no flowers.

Once flower buds form, increase water and temperature. Once the buds set, night temperatures of 60 to 70 °F are ideal. By mid-November your cacti should be in full bloom.

Plants may drop buds if temperatures are too high or humidity too low. They may not flower if temperatures are too high for long periods. Falling or yellow leaves may result if plants are too dry or they get too much sunlight. Low humidity and too much water can stimulate root rot.

TYPES OF RAIN FOREST CACTI

Thanksgiving and Christmas Cacti (Schlumbergera truncata and S. x buckleyi): Thanksgiving and Christmas cacti flower anytime between those holidays on 1-to-2 year-old plants. The Christmas cactus has smaller, smooth-edged stems. Thanksgiving cacti have segments with toothed or jagged edges. Flowers appear earlier under natural light conditions than those on S. x buckleyi. Many cultivars are available.

Easter Cactus (Rhipsalidopsis species): Easter cactus bears flowers at the stem joints and at the ends. They should to be treated the same as other holiday cacti but at different times of the year. The resting period for this group is from December through late March when plants should be kept cool and dry until the flower buds form. Once the buds form, the plants can be give more water and light. The plant flowers from early April until late May. Numerous cultivars are available.

Orchid Cactus (Epiphyllum species): Orchid cacti prefer temperatures that range between 45 and 70 °F. They will tolerate extreme heat if well-shaded and the humidity is high.

Plants should receive balanced fertilizer once a month from spring to fall. It is always better to use too little fertilizer than too much. To encourage flowering use an application of low nitrogen fertilizer once at the end of February and again in early November. Do not fertilize plants during December or January.

The major flowering season for day-flowering orchid cacti is from April to June. Night-blooming species flower in late summer and early fall. Epiphyllums will flower when they are 2 to 3 years old. Make sure that your plants have a nighttime temperature of 40 to 50 ° F during the winter. Plants like to be rootbound before flowering.

Orchid cacti have flattened, fleshy stems, often deeply toothed, with a trailing growth habit. Flowers are 6 inches long or more and of many colors. They are often sweet-scented and night-flowering. There are hundreds of cultivars.