CORVALLIS, Ore.— Decorating with poinsettia plants or giving a Christmas cactus to a friend are holiday traditions for many, but not everyone is aware that there's more to these popular indoor winter plants than their bright leaves and cascading blossoms.
Poinsettia is a common name for Euphorbia pulcherrima, a member of the spurge family, according to Linda McMahan, horticulturist for the Yamhill County office of the Oregon State University Extension Service. The plant goes by many common names worldwide, including Easter star, lobster flower, flame-leaf flower, crown of the Andes and noche Buena, she said. Its wild habitat is as close as Mexico.
A large propagation industry based in California grows up to 200 varieties for holiday decoration, McMahan said, and sales approach 100 million plants each year.
Although they are not hardy below about 50 degrees, the poinsettia's sturdy nature and colorful flowers and foliage make it a perfect seasonal indoor plant for northern climates. Breeding and propagation techniques have produced compact plants that are full and lush through the holiday season, but make it a difficult plant to keep going at other times of the year.
"In the wild, the shrub grows to 10 feet tall, and its typical bright red leaves 'bloom' near the end of December," McMahan said. "It has a somewhat open, gangly form, unless pruned. The actual flowers are yellow or green, inconspicuous and found at the center of a group of large colorful leaves, known botanically as bracts."
As the holiday season progresses, many of the flowers fall off, leaving only small stumps, but the flowering bracts persist much longer.
"This season, look carefully at the colorful bracts and compare their vein structure to green leaves. Without the color variation, the two would be nearly indistinguishable. The amazing color show is to attract pollinators, especially hummingbirds, to the red coloration," McMahan said.
The whitish, milky poinsettia sap can be irritating, especially to the eyes, and can trigger allergies in some people, although the plant is not considered to be highly toxic, McMahan said.
Holiday cactus is another seasonal favorite. It also has other common names, including orchid cactus, Easter cactus, Christmas cactus, Thanksgiving cactus, and flora de maio (May flower).
"Color range and form are astounding," McMahan said. "Unlike poinsettia, the cactus can live past the holiday season and make good, year-round house plants, often providing surprise blooms at various times of the year."
People often question if it's really a cactus "The answer is yes, although it grows in the wild of the tropics in trees, where it is closer to the sunlight. Botanically, it is an epiphyte, a Greek word meaning something that grows perched on another plant," McMahan said. One major habitat is the high mountains of Brazil.
Segments of the stem can be separated and placed in water or moist soil, and new roots will grow from the base.
"In my living room resides an older variety with a span of about three feet — a cutting from my mother about 40 years ago," McMahan said. "Its flowers are a bright, fuschia/magenta color, each seeming to last only a few days. It blooms anytime between December and January, so long as I remember to leave it in a room where the lights are off in the evening."
Flowering is triggered by shortening nights, and flashes of light at the wrong time can throw off its biological blooming-time clock. Flowering is also triggered by lower temperatures; a spot right next to the fireplace or furnace vent might not be the best choice. For directions on how to induce flowering or keep the cacti as longer-term houseplants, check Web sites for details. A good one is Purdue Extension's Christmas Cactus FAQs.