I read your article in the Las Cruces SunNews and wondered if you have any advice on how to get my wife's poinsettia plants to recover after they bloomed over the holidays. They have dropped most of their leaves now. The article indicated pruning back the old stems to promote new growth to make cuttings for propagation. I am assuming I should do the same to get the plant to recover, but wonder how far back to cut them.
I'm glad last week's article was interesting and stimulated your question. Yes, you are correct, you can prune the stems after the poinsettia plants have completed their flowering and dropped their leaves and bracts (the colorful leaves below the true flowers).
The fact that the leaves fell from the plant indicates the plant experienced some environmental stress. This stress could have been low temperatures, too little light, or drought. Correct the environmental deficiency before you begin encouraging growth. It is possible to maintain the plant in a semi-dormant stage for a while if it is not appropriate to encourage growth now. After the leaves have fallen, keep the plant cool (50 degrees F), and provide only a little water to maintain this dormant state. When you are ready to encourage the plant to grow, place it in a bright location, increase the temperature to 70 degrees, and increase water slightly. Prune the stems back to leave 3 to 6 inches of stem. You can prune interior stems to remove them completely as they will be crowded and not receive enough light once the other stems grow.
In a few weeks you should see new sprouts developing from the buds on the stems. Increase the quantity of water applied as the new leaves form. You can begin fertilizing lightly after growth begins.
When the weather is warm enough (no chance of freezing), you can move the plants outside for the summer. Put them in a location with protection from direct sunlight during mid-day and afternoon. Protect them from the winds that are so common in the spring, and do not let them become too dry. If there are too many new stems forming, you can thin them by removing some of them. This is a good time to try propagating them to make new plants if you want to try increasing the number of plants. As the plants continue growing, increase fertilization using a houseplant fertilizer high in nitrogen that stimulates new growth. Follow the label directions on the fertilizer container when fertilizing.
Pinch the tip of the stems as they reach 6 to 8 inches. This will encourage branching and result in many more flowers (and colorful bracts) next winter. In the late summer, change from a high nitrogen fertilizer to one with a higher concentration of phosphorous. This will encourage the formation of flower buds.
As mentioned last week, information about day length treatments in the autumn to stimulate flower bud formation is available in the Yard and Garden archives on the NMSU College of Agricultural, Consumer and Environmental Sciences web site (http://cahe.nmsu.edu/ces/yard/2008/).
For more gardening information, visit the NMSU Extension publications World Wide Web site at http://www.cahe.nmsu.edu/pubs/_h.
Send your gardening questions to:
Yard and Garden, ATTN: Dr. Curtis Smith
NMSU Cooperative Extension Service
9301 Indian School Road, NE, Suite 112
Albuquerque, NM 87112
Curtis W. Smith, Ph.D., is an Extension Horticulture Specialist with New Mexico State University's Cooperative Extension Service. New Mexico State University is an equal opportunity/affirmative action employer and educator.