The Essential Upgrade Pack turns the second edition of Viticulture into the Essential Edition. You do not need the upgrade pack if you own Tuscany.
The upgrade pack includes the following. Add these items to your copy of Viticulture (replace all previous visitor cards with the cards in this pack):
36 Mama and Papa cards
18 Field cards
38 Summer Visitor cards
38 Winter Visitor cards (see full image of all essential visitors here)
24 Automa cards
1 rulebook (the rulebook does not include Automa rules, but they can be found here)