What does "stirth'" mean?

Question

Or "stir th'" (where I saw is printed as "stirth'"). It's from a poem from Henry Wotton.

This day Dame Nature seemed in love;
The lusty sap began to move;
Fresh juice did stir th’ embracing vines,
And birds had drawn their valentines;
The jealous trout that low did lie
Rose at the well-dissembled fly;
There stood my friend, with patient skill
Attending of his trembling quill.

On a Bank as I Sat A-fishing
Sir Henry Wotton (1568–1639)

http://www.bartleby.com/331/29.html

Answer 1

The line is:

Fresh juice did stir th’ embracing vines,

In this case, th’ is simply a poetic abbreviation for the:

Fresh juice did stir the embracing vines,

This avoids an extra syllable (and keeps the poem in iambic quadrimeter).