Cacti are fascinating plants. Thanksgiving cactus (Schlumbergera truncata) and Christmas cactus (Schlumbergerz x buckleyi) are popular fall and winter-flowering houseplants.

Thanksgiving cacti normally flower near the Thanksgiving holiday, about a month before the Christmas cacti bloom. Flowering can last up to seven to eight weeks. Thanksgiving cacti actually inhabit the tree tops of southern Brazil, sharing space with orchids and bromeliads.

Christmas cacti were hybridized in 1840; the genus was named after the Belgian horticulturist, Frederick Schlumberger. The common names became associated with the holidays based on when they bloom. Cultivars are available in a wide variety of colors including red, rose, purple, lavender, orange and white.

To tell the difference between a Thanksgiving and Christmas cactus, look at the shape of the flattened stem segments. On a Thanksgiving cactus, the stem segments each have two to four saw-toothed serrations along the margins. On a Christmas cactus, the stem margins are more rounded. A second way to tell the difference is to look at the color of the pollen-bearing anthers inside the flowers. The anthers of a Thanksgiving cactus are yellow whereas the anthers on the Christmas cactus are brown.

Holiday cacti care

Holiday cacti initiate their flower bud development as the days get shorter and as temperatures get cooler.

These plants need longer nights with no light versus actual sunlight to set flower buds. Twelve to 14 hours of darkness each day starting about the middle of September and lasting for four to six weeks will initiate the bud set.

Buds will normally be visible in three to four weeks. Once buds are set and ready to bloom, holiday cacti bloom best in a part-shade spot; direct sunlight may cause leaf segments to look pale and yellow.

Keep temperatures cool, between 60 and 70 degrees F. Fertilize plants monthly when new growth starts in late winter or early spring; use a general-purpose fertilizer at half strength.

Do not fertilize during flower bud formation. These plants prefer to be evenly moist. Do not let soil stay waterlogged; don’t let the soil completely dry out either. A light potting mix works best; these plants will not do well in a heavy, wet potting soil. You can also purchase potting soil designed especially for cacti.

Problems

One of the most frustrating things is to have flower buds fall off the plant before they open and bloom. Several different conditions can cause this: over-watering, insufficient light, or moving the plant during bud development. Avoid moving plants until the buds are well developed and the plant is flowering.

Drafts and temperature fluctuations can also cause premature flower bud drop. Newly purchased plants that are in bud will most likely drop a few buds due to the abrupt changes in transport.

Resist the temptation to repot holiday cacti; they prefer being pot-bound. If you do repot, definitely wait until after the plant flowers. Pruning the plant after blooming will encourage the plant to branch out. Do this by removing a few sections of each stem by pinching or cutting. You can root the cuttings easily in moist potting soil or in water to produce more plants.

Once you have one of these plants, you’ll want more! Give them a chance and add them to your houseplant collection!