Lobster Cactus Schlumbergera truncata

The Thanksgiving cactus or crab cactus is a tough epiphytic succulent that has showy flowers that bloom in the winter, usually around Thanksgiving, hence its most popular common name. It is also known by many other common names and is sometimes confused with the true Christmas Cactus (Schlumbergera x buckleyi). You can tell them apart because the Thanksgiving cactus has claw-like appendages on its flat stems (or cladodes) that resemble crab claws, hence the common name crab cactus. The Thanksgiving cactus is native to the rainforests of Southeastern Brazil and grows in the coastal mountains on trees or rocky areas. It is a member of the cactus family (Cactaceae). The specific epithet, truncata, means "to cut off square" and references its stems.

This plant prefers partial shade and temperatures between 70 to 80 degrees Fahrenheit. It is best planted in a moist, well- drained cactus or  succulent potting mix and placed in a warm room that receives bright light in the winter and high humidity. In the summer. It will need some shade or the stems will turn yellow. Because of their high humidity requirements, bathrooms are a popular spot for growing this plant. Avoid overwatering. If you are lucky it will bloom a second time as the days lengthen in February. You can also force it into blooming by exposure to night temperatures of 40 degrees for several successive nights. When new growth starts in the spring, fertilize monthly, reducing fertilizer in the fall and early winter. Repot the plant every three years or so, as it does well being slightly pot-bound.  It is easily propagated by stem cuttings. Remove two or three stem segments with a sharp knife and let it callous over for a few days. Plant the stem segment in moist, well-draining potting mix and water when the potting mix is completely dry. The stems will take root after a few weeks.

The Thanksgiving cactus has a multi-branched, bushy, pendulous and cascading habit. It grows up to 12 inches tall and 24 inches wide. The green stems are flattened, segmented, and spineless. They have pointed, claw-like projections on the stem margins. The blooms are erect, tubular, and do not hang down like the flowers on Schlumbergera x buckleyi.  Flowering occurs in late November. They are available in vibrant shades of red, purple, orange, pink, and creamy white.

Most of the plants sold in stores today are the sterile hybrids (S. x buckleyi) of Christmas cactus (S. russelliana) and Thanksgiving cactus (S. truncata). There are over 200 cultivars of these plants giving a variety of flower colors.

The Thanksgiving cactus is frequently grown in containers or baskets. It is a popular houseplant around the holidays and makes a wonderful gift. In warm climates, this plant could also be grown outdoors in a rock garden. It does not do well in hot arid environments like other cacti. It can grow outside in zones 10 through 12, but in colder zones, it must be grown as a houseplant.  

Quick ID Hints:

• Cladodes with acuminate teeth, pointed claw-like projection on the margins of the stems
• Flowers elongated tube, zygomorphic
• Flowers in shades of pink, orange, or white, apex strongly oblique, yellow anthers
• Fruits are smooth, red, round to pear-shaped, and not ribbed

Insects, Diseases, and Other Plant Problems:  Aphids, red spider mites, scale and mealybugs are common insect pests.  Root rot can be a problem for overwatered plants. Gray mold can occur in high humidity and poor air circulation.  Reduced flowering or dropping of flower buds can be from inadequate dark hours (at least 13 uninterrupted hours), sudden temperature changes, lack of moisture, or light changes. Direct sunlight can scorch the stems. 

VIDEO Created by Elisabeth Meyer for "Houseplants, Succulents, and Cacti", a plant identification course offered in partnership with Longwood Gardens.

More information on Schlumbergera.