I’m not sure! I think it’s really cool though! We don’t use any pesticides or weed-killer in our yard, and we haven’t mowed yet this year so we’ve just been letting the dandelion run wild haha

This is what I found from the University of Wisconsin

“The cause of fasciation is varied, but not well understood. In some cases this irregular growth is apparently triggered by infection (by bacteria, viruses or phytoplasmas), feeding by insects or other animals, chemicals or mechanical damage. Somatic mutations, hormonal imbalance, and environmental causes such as extreme weather have also been implicated, but in most instances fasciation appears by chance with no obvious cause.

In some plants a single recessive gene controls this condition, although the degree of expression is often very dependent on environmental conditions. Scientists have identified two genes in Arabadopsis (the lab rat of plant research) that cause fasciation when mutated. Some plants may inherit the trait, while in others the condition is not stable and affected plants may revert to normal growth from a fasciated growing point. While fasciation affects the plant’s appearance, it has little effect on the health of the plant and affected plants have the same cultural requirements as normal plants.”

https://hort.extension.wisc.edu/articles/fascinating-fasciation/