Do I need an apostrophe in “These trees’ roots”?

Question

Do I need an apostrophe in "These trees’ roots"?

For example,

"Wow!!! These trees' roots are so long!"

In this example the speaker can see both roots and the trees themselves.

Answer 1

Yes, you need the apostrophe. -s' denotes possession of some thing or things by multiple owners. The roots belong to the trees; the trees own the roots. Therefore, the roots are the trees' roots.

Answer 2

Yes, you need the apostrophe, and you need it right where it is: make sure that the apostrophe is after the "s", not before.

-s' is the possessive ending for plural nouns (e.g. trees becomes trees'), while -'s is the possessive ending for singular nouns (e.g. tree becomes tree's).

Hence, The roots of these trees becomes These trees' roots.

And The roots of this tree becomes This tree's roots.