org-yank-folded-subtrees

org-yank-folded-subtrees is a variable defined in `org.el'.
Its value is

t

Documentation:
Non-nil means when yanking subtrees, fold them.
If the kill is a single subtree, or a sequence of subtrees, i.e. if
it starts with a heading and all other headings in it are either children
or siblings, then fold all the subtrees. However, do this only if no
text after the yank would be swallowed into a folded tree by this action.

You can customize this variable.