Palm trees

(Read in a mellow voice)...

Palm trees are 1 of the most calming trees I know of simply because:

The leaves:

If you notice that Palm trees how their leaves move in a swaying motion

in a kind of slow motion pace.

The motion;

Look at this.

It's a relaxing swaying type motion.
Look at how slow the leaves move.

The #1 place where they are found...
Beaches! If you notice the most Palm trees are found in Beaches or even islands (Hawaii)