Did you purchase a poinsettia to decorate for the holidays or receive one as a gift? If so, you are in good company. The poinsettia (Euphorbia pulcherrima) is the No. 1 flowering potted plant sold in the United States, even though its usual sales period only lasts for the six weeks before Christmas.
This beautiful plant is native to tropical forests of southern Mexico and Central America, where it grows in the wild as a bush or a small tree. It was brought to the United States in 1825 by Joel Roberts Poinsett, our first ambassador to Mexico and an avid amateur botanist.
What most people call poinsettia “flowers” are really bracts, or modified leaves. The actual flowers, called cyathia, are small yellow structures at the center of the bracts. The plant drops its leaves and bracts soon after the flowers shed their pollen. If you want to keep the colorful bracts and leaves on the plant as long as possible, you need to delay maturation of the flowers. With care, poinsettia bracts can be maintained until Valentine’s Day.
To keep poinsettias flowering, provide them with six to eight hours of indirect light per day. They should not be exposed to drafts or sudden changes in temperature. Daytime temperatures of 60 to 70 degrees F and nighttime temperatures of 55 to 60 degrees are ideal. Do not expose them to temperatures below 50 or above 70 degrees or it will shorten the blooming period. Water them when the soil is dry but do not saturate them. They are very sensitive to overwatering and easily succumb to root rot. Apply a water-soluble fertilizer once a week until the leaves begin to fall off, then reduce watering. The bracts will be the last leaves to fall.
Many people discard their poinsettias at the end of the holiday season. The plants are relatively inexpensive, and they are fussy about growing conditions. But if you have an interest in this unique tropical perennial, you can coax them into bloom in future years.
Once the bracts begin to fall, cut the plant back to about 6 inches high and place it in a cool, dark place for six to eight weeks. Keep it fairly dry, but don’t let it wither. In April, repot it in fresh potting soil, apply a water-soluble fertilizer and place it in a warm, sunny spot to encourage new growth. Water it when the soil surface becomes dry.
Once all danger of frost is past, you can take your poinsettia outside and grow it in partial shade. Poinsettias are attractive to whiteflies and other insects, which should be controlled promptly. Remove any weak shoots and pinch back long shoots to keep the plant bushy.
After the autumn equinox in late September, prepare your poinsettia for flowering. The plant will need full sun during the day, and at least 14 hours of total darkness at night. You can place it in a closet or cover it with a box for the night. A better solution is to put it in a room that isn’t used at night. Unscrew the light bulbs or tape over the switch to avoid accidentally turning on a light. Any stray light can delay or prevent flowering, including a porch light or headlights from a vehicle that shine through a window.
If all goes well, the bracts will begin to color by the end of November, and you can once again display your beautiful poinsettia for the holidays. And even if it fails to bloom, it still makes a lovely foliage plant through the summer.
A WSU Master Gardeners of Chelan County column appears weekly in The Wenatchee World. Connie Mehmel is one of four columnists featured. To learn more, visit wwrld.us/cdmg or call 667-6540.