Care of Poinsettias in San Antonio

December 14, 2007

Plant of the Week

David Rodriguez

poinsettiasPoinsettias are one of the most readily recognized symbols of Christmas in America. There are now intense red, pink, light red, white, salmon, yellow and bicolor (white or pink speckles on red) varieties. If you want maximum decorative use of poinsettias during the bloom period, keep the soil moist, but do not over water. Usually, a thorough watering once per week is sufficient. Add water until the first evidence of moisture reaches the pot’s drain holes.

Hot or cold drafts shorten the life of your poinsettia. Keep it in a spot with good light, but avoid direct sunlight during the bloom period. The bloom usually lasts for six-to-eight weeks. At that time, the plant and potting mix can make a good addition to your compost pile.

Some gardeners, however, are determined to grow the plant through the year and bring it into color for next Christmas. If you have that ambition, here is a plan that works for the San Antonio area:

1. About six weeks after Christmas, when the colored bracts lose their appeal, reduce watering to about once every three weeks. Water just enough to keep the stems from shriveling. Place the plant in a cool (60-70 degrees F), well ventilated location. Avoid bright sun but otherwise, light is not a major factor during this period.

2. In mid-April the plant should be cut back to six inches high and repotted in a container one or two inches larger in diameter than the original pot. The extra space in the new pot can be filled with a commercial potting mix or a homemade soil mix (peat, sand and garden soil works well). The repotted plant should be placed outside in a location that receives morning sun but afternoon shade. It should be kept moist and fertilized every two weeks with one of the complete water soluble fertilizer mixes. Apply the amount recommended on the label. The growth during this period needs to be controlled by pinching back the top so that only three or four leaves are maintained on each shoot. The pruning should be continued until mid-August.

3. In mid-August, bring the poinsettia inside to be placed in a sunny window that doesn’t get too hot. A temperature between 65-70 degrees F. seems to be best. Adjust the watering frequency to fit the new conditions.

4. The unusual part of the poinsettia growing process begins in October. The poinsettia now needs to be subjected to a strict light regime, if it is to be at it’s colorful best at Christmas time. From the first week in October until Thanksgiving the poinsettia needs to be placed in complete darkness from 5 p.m. to 8 a.m. Choose an unused closet or pantry as the darkroom. A card board box cover in a cool corner of the room will also work. Any exposure to extra light will delay the bloom. Conscientious fertilization, watering, and placement in a sunny window must continue through the dark period and until mid-December if maximum development is to be achieved.

A native of the American tropics, poinsettias can be set out in a warm, sunny part of the garden in April. But, not being cold hardy, the poinsettia must be protected from winter cold or it will freeze.

Remember, Learn and Have Fun!

David Rodriguez is County Extension Agent-Horticulture, Bexar County. For more information, call the Master Gardener ‘Hotline’ at (210) 467-6575 or visit our County Extension website at, click under Horticulture and Gardening.

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