We saved this plant last Christmas, repotted in the spring and it became about 18″ tall. Did well, but now leaves are yellowing and curling. Too much water or not enough? Also had white bugs and I used Safer’s soap. Can this plant be saved? Can’t attach a sized photo Judy Miller
Thank you for consulting Toronto Master Gardeners.
You have already done quite well with your year-old poinsettia, as these are not easy plants to keep for more than one season. However, it may be possible to carry on longer, if you “manage your expectations”, as they say.
There are a number of problems that might cause yellowing leaves: too much water, too little water, mineral deficiencies, too much sun, too cold (unlikely in the house), or certain diseases. By far the most common of these is too much water. Does the new pot have good drainage? Only water if the soil is dry an inch below the surface (just stick your finger in), and make sure the plant is never sitting in water. Poinsettias like 6 hours of indirect light, and don’t do well in drafts, either hot or cold. Yellowing leaves can also result from a lack of magnesium and molybdenum, but if you recently repotted it in good loamy soil, it probably does not need feeding right away. Normally you would only feed it when it is growing vigorously, but even now a small amount of a well-balanced plant food once a month might help.
You don’t say whether the Safer’s soap dealt successfully with the bug problem, but here is a link to a discussion of white fly and/or mealybugs. It happens to be about hibiscus, but would apply to poinsettias too: https://www.torontomastergardeners.ca/askagardener/hibiscus-problems/
If you are hoping to get red bracts again, be aware that the plant needs 14 hours of complete darkness for this to start. You could cover it with a black cloth, or put it in the closet for that long every night.
Here are two more informative links that have more details about watering, bugs and other issues:
https://www.torontomastergardeners.ca/askagardener/poinsettia-re-potting/
https://gardenforindoor.com/poinsettia-leaves-turning-yellow/
Good luck!
January 29, 2021