Poinsettias are tropical plants, and aren’t at all cold-hardy, but can survive quite well year-round outdoors in southern climates or just for the summer in colder regions. They are best suited to USDA zones 9 to 11. Plant outdoors after the last frost danger is past, and choose a spot where the plant will get plenty of morning sun, but has light or partial shade in the hot afternoon.
With poinsettias, you must balance its needs between water and sun. They like soil that is somewhat cool and evenly moist, so the partial shade is best. However, it’s not a wetland plant, so don’t pick a spot where water will stand or puddle. The soil should be well-drained and rich.
Mulch around the base of poinsettias outdoors, to help retain soil moisture and keep the soil cool. Fertilize once a month with liquid fertilizer if your soil is not very rich with organic matter. If you do have rich soil, you probably won’t need to fertilize more than once; do this at the start of the spring growing season.
Water when the soil at the base of the plant is dry to the touch. In the late fall or early winter, cut back old growth on the plants to encourage stronger new growth in the spring. If you want more flowers, pinch off terminal shoots occasionally through the spring and early summer.
Getting poinsettias to turn their signature red holiday color is difficult. This requires them to be in total darkness for 14 to 16 hours a day. The recommended time frame for this is from 5 p.m. to 8 a.m., when temperatures are cooler. The ideal nighttime temperature for flowering is between 55 and 60 degrees Fahrenheit, and temperatures warmer than 70 degrees can instead cause decay.
This will mean you will have had to bring them indoors in the fall, and the darkness should be imposed around October 1, to make them flower in December. A closet without a heating vent is a good location to keep them in darkness, perhaps with black plastic or opaque fabric coverings. Bring them out into sunlight for at least six hours during the day.
Poinsettias are usually propagated by cuttings. Take 8-inch cuttings from the tips of poinsettia stems in the summer, and dip them in rooting hormone such as that available for rose cuttings. Alternately, an easier method is to take woody stem cuttings, about 18 inches, place in rich soil, and keep moist, but not wet, for several weeks.
Do this early enough in the summer that you don’t risk frost damage to the young cuttings, or bring them inside if this is done late in the year. They are fast-growing; the standard pot-size poinsettias sold in stores around Christmas are forcibly small, and will grow many feet tall when planted outdoors.
Poinsettia Pests and Diseases>
Poinsettias are susceptible to root knot, but this can be avoided by proper mulching and watering. They also are bothered by bacterial or greasy canker, both caused by conditions that are too warm and moist. Rot at crown, collar or root also will emerge in wet, warm conditions.
If the plant is too cold and too moist, you may risk gray mold on the soil and stem of the poinsettia, which can be avoided by proper temperatures and good air circulation. Mildew and stem rot can happen when the plant becomes overcrowded with foliage and stems; avoid this by regular pruning.
Want to learn more about poinsettias?
Check out these Web sites chosen by us for more information on the subject:
The University of Illinois Urban Extension has FAQ on poinsettias.
Poinsettia history and care in Southern gardens from Florida.
The Center for Integrated Pest Management from the University of California details signs and treatments for many poinsettia problems.