Mr. Grow's Tip of the Month
February 1997
'Keeping a Poinsettia until next holiday season'
Euphorbia pulcherrima Poinsettia
Culture:
Poinsettia is a native of Mexico and can grow to 8-10 feet tall in the wild. In the U.S. they are considered the symbolic plant of the holidays and are grown to remain under 3'. They prefer a humid environment and a temperature of 67f during the day, 45f at night.They prefer bright indirect light. Poinsettias can be fertilized year-round but more heavily in late summer(short break in April and May). Some of the major problems with Poinsettias are cool or warm drafts and improper soil moisture. If the soil is too wet, crown or root rot will set in, if it is too dry the plant will drop leaves and have poor flower color. Discard drainage water in saucers to prevent root rot.The soil should always be moist but not soggy. The plant can easily be propagated with cuttings taken in the spring or early summer. Repotting can be done in late summer just before it goes into a flowering light schedule, or in late spring just before the rush of new growth emerges. White flies can be a serious threat, spray with insecticidal soap, repeated treatments are usually necessary.
Keeping a Poinsettia alive throughout the year:
During the Holidays -> December-January
Place the plant in a bright sunny window for everyone to enjoy.. If you live in an older house be careful of drafty windows. Also be careful of heating registers and fireplaces, if the temperature around the plant goes above 70-72f the flower bracts will fade. At this time of the year the plant needs very little care. Fertilize with a half strength all-purpose fertilizer to keep the flower color going thru January.
Fertilize at half strength once every third watering. When flower bracts show signs of fading it is time to put the plant into dormancy. Some plants won't start to fade until late March others may turn in early-mid February. There are a few simple things you need to do to induce dormancy. First, is to heavily prune the plant back to about eight inches tall, leaving one or two leaves per branch.See picture. The branches that are cut off can make good stock for propagating. It may be a good idea to wear gloves while pruning, members of the Euphorbia genus have a white milky sap that is irritating to the skin for some people. After pruning, cut back the amount of water so that the top inch (2cm.)of the soil is dry between watering ( no fertilizing).
By mid-late April increase the frequency of watering and fertilize with (12-12-12 or 20-20-20). By late May the plant should be growing vigorously. This is a good time to up-pot if needed.(I personally would recommend a repotting now because it gives the roots a fresh environment to grow and support new growth.Potting soil can build up salt quickly in a container. The plant will enjoy the fresh, pH neutral soil.)By June it should be warm enough to put the plant outside if you want. But be careful to shelter it from drying winds and keep a close eye on soil moisture.
Keep on your schedule of watering and fertilize about every other watering with half strength. In mid July the branches will need to be pinched back about 2-3" to promote a short dense habit. This is the season of White Flies, be careful to check plants before you bring them indoors in late summer. It is better to identify a pest problem early and be able to treat the problems outdoors and bring in a clean, healthy plant. Starting in mid-late September you will need to do alittle more work. The Poinsettia plant is photoperiod sensitive which means that the plant is triggered to flower by the decrease in the length of light. Sensing that the days are shorter the plants puts all it's energy into reproduction (flowers and stamen).The poinsettia will set flower buds only after being exposed to the short day (10 hours of light or less) for about 10 weeks. This can be very tricky because the light cycle has to be very strict. Exposure to a 60 watt light bulb for ten minutes is enough to disturb the flowering cycle. An unused closet or large box is ideal for isolating a plant overnight. Each morning bring out the plant and place it in a sunny window where it will stay very close to 70f.
Autumn-> October-November
Keep fertilizing and watering as usual. Make sure that the plant is not too cold during the long nights. Temperature at nights should be 45-55 f. After 9-10 weeks, mid-late November, the bracts should start to develop and at this point you are done. Bring the plant out to the normal household light and enjoy the year-long work you have accomplished! It may seem like alot of work when you could have just bought a new poinsettia for $8, but it is so much more satisfying to display a plant you grew yourself.
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