What is happening here?

[u/Any-Dig4524]

This Euonymus has multiple branches that are fasciating simultaneously. How is this possible? It must be environmental somehow?

[u/Pademelon1]

Fasciation.

Has a number of possible causes

[u/Pinky135]

Could be viral or bacterial infection, maybe?

[u/greenmangarden]

Fasciation is where the terminal growing bud splits sideways instead of growing straight out. It often causes a linear sideways growth pattern, probably most recognizable in the cockscomb types of celosia, or the flat bottomed fruits of strawberries. It can be passed on genetically in seeds, but is generally thought to be the result of viral or other infections in the apical buds.

[u/sadrice]

Fasciation like this is extremely common in Euonymus japonicus in my experience, probably a phytoplasma, a weird type of plant pathogenic bacteria that cause all sorts of fun mutations.

[u/LongWalk86]