White flowers of Christmas cactus are a favorite with many gardeners. (Photo by Allen Owings, LSU AgCenter) Christmas cactuses like well-drained containers and thrive on outdoor patios for most of the year. (Photo by Allen Owings, LSU AgCenter) News Release Distributed 12/17/15
By Allen Owings
LSU AgCenter horticulturist
HAMMOND, La. – Although poinsettias are typically associated with the holidays, another group of plants to consider are the Thanksgiving and Christmas cactuses. These are highly recommended for long-term enjoyment.
Christmas cactus is probably the most popular of the holiday cactuses and was a favorite house plant for the season in previous years. Christmas cactus is known by the scientific name Schlumbergera bridgesi. Thanksgiving cactus is a related species and is sometimes called crab cactus. Its scientific name is Schlumbergera truncata.
Thanksgiving cactus blooms from October to November and has rather flat, glossy green leaves that are distinguished by two prominent teeth (claws) at the growing tip. Flowers are usually scarlet.
Christmas cactus is distinguished from the Thanksgiving cactus by its rounded leaves with blunt tips. Flowers are carmine red with a purple tinge in the center.
Another holiday cactus that blooms later in spring is the Easter cactus. It blooms in March and April and is scientifically classified as Rhipsalidopsis gaertneri.
Easter cactus has long, flattened joints, dull green leaves with rounded edges and a few bristles at the growing tips. Flowers are a deep scarlet and star-shaped. In addition, they are symmetrical, which distinguishes them from other holiday cactuses.
You can find many hybrids that feature different growth habits, foliage characteristics and flower colors not seen in older varieties.
Most holiday cactus flowering is regulated by day length and temperature. Christmas and Thanksgiving cactuses bloom because of shorter fall days and cool nights. These same conditions cause bract coloration and flowering in poinsettias.
Thanksgiving cactus sets buds as early as mid-September, with major flowering in October and November. Christmas cactus has bud set by late October or early November with major flowering around Thanksgiving and continuing through early January. Flower buds of Easter cactus develop more slowly and will not appear until late winter or early spring.
After cactuses finish flowering, they produce new vegetative growth. The new growth helps buds develop for the next bloom cycle. Water and fertilize the plants more during this active growth period. In mid-August, water and fertilize less to harden off the new growth and increase the opportunity for bud development in the fall.
Holiday cactuses thrive in a well-drained, sterile potting medium that is high in organic matter. Sand may be added to increase the weight of the medium. A soil pH of 5.5-6.2 is optimal for growth. Clay pots are great for cactus because they are porous and allow the soil to dry out somewhat between waterings.
As plants develop new branches and buds, they often become top-heavy and difficult to handle. Use a wide, short pot to assist in balancing out any top-heavy growth that the cactus produces.
Fertilize until flower buds appear. Use a good soluble fertilizer, such as 20-20-20. Be careful not to overwater. This is a major problem. Maintain temperatures between 70 and 80 degrees for ideal growth. A cactus will tolerate 90-100 degrees, but it will grow slower. Avoid direct sun exposure during late spring and summer.
You can see more about work being done in landscape horticulture by visiting the LSU AgCenter Hammond Research Station website. Also, like us on Facebook. You can find an abundance of landscape information for both home gardeners and industry professionals at both sites.
Rick Bogren