Upward leaf cupping on poinsettias (seen here) can be caused by improper use of Insect Growth Regulator (IGR) Distance. The Distance label states: In a few instances, malformation of roots and newly expanded leaves (i.e. cupping), has been observed on certain poinsettia varieties (i.e. Freedom Bright, Freedom Bright Red, Winter Rose and Jingle Bells) following drench application of distance. Leaf malformation was more commonly observed on plants exposed to high air temperatures and on plants whose soil media was allowed to dry out following application, such as those along walkways or near doorways. Malformation of new leaves was permanent, but new growth was unaffected after plants were hydrated. Malformed leaves are generally not evident at time of shipment.
Upward leaf cupping is also caused from phenoxy-based herbicides such as 2,4 D, however an improper drench application of IGR Distance can cause injury. Follow label suggestions on ways to minimize this risk and read labels carefully before application. Do not apply Distance to poinsettias after bract formation and note that reduced efficacy has been observed with the Q Biotype with this IGR.