What does idiom shakes like a tree mean?

The idiom "shakes like a tree" doesn't exist in the way you might think. It's not a common phrase in English.

Perhaps you're thinking of a similar idiom: "trembles like a leaf." This idiom means to shake or shiver uncontrollably, usually due to fear, cold, or weakness.

For example: "He was so scared, he trembled like a leaf."

If you can provide more context about where you heard this phrase, I might be able to help you figure out what it means.