This photo was submitted by a grower the first week of October. It shows leaf-like enations, ruffled leaf tissue that appear on the interveinal leaf tissue on the underside of the leaf.
It has been reported that enations on poinsettias are usually the result of airflow across the leaf surface during periods of high heat. It is thought that high heat during August may have been the cause on a few plants in this case.
Various types of other leaf deformations (photo) may occur on poinsettia. Often, the damage begins when the leaves are very small. As plants grow, the mature leaves cover the damaged young leaves, so plants are still marketable.
Branches that develop after pinching may develop a few distorted and misshapen leaves. Environmental stresses, overhead fertilization with phosphorus fertilizers, or abrasion may lead to distorted leaves. This season, the very warm temperatures in early August, may have contributed to this phenomenon. Changes in temperature and humidity as plants are moved from propagation to finishing houses lead to leaf distortion. It is thought that rapid changes in humidity, result in an accumulation of salts along the leaf margins and veins, resulting in leaf injury. This distortion becomes apparent as the injured leaves grow and expand.
Resources:
The Effects of Heat Stress on Poinsettias (2011)
High Temperature Stress on Poinsettias (MSU)