The Characteristics of the Sylvan Monsters
The Sylvan Monsters all generally have an effect that when you reveal a Plant-Type monster from the top of your Deck, you send that monster to the Graveyard, and it returns a card to the bottom of the Deck (in the order you choose if it’s multiple cards) when it’s not a Plant-Type monster!

Also, each of them has an effect that triggers when they’re sent from the Deck to the Graveyard by a card effect that excavates, so the “Sylvan” monsters are able to work in tandem with them.

Let’s Look For Compatible Cards!
Using the Card Database, look for cards that work with these cards

What kind of cards will you add to your “Sylvan” Deck?
It’s recommended you add in Plant-Type monsters! By using Level adjusting Tuners like “Spore” and “Copy Plant“, you can build an interesting Deck that Xyz AND Synchro Summon!

Also, check for cards that can dump a huge number of “Sylvan” monsters to the Graveyard instantly, such as “Magical Merchant“!

Let’s Search the Card Dataase
– Cards whose text includes “Excavate”, “Graveyard”, and “Send”
– Cards whose text includes “Plant-Type monster” and “Special Summon”
– Plant-Type monsters
– Rank 1 Xyz monsters
– Rank 2 Xyz monsters
– Rank 3 Xyz monsters
– Rank 4 Xyz monsters
– Rank 6 Xyz monsters
– Rank 8 Xyz monsters
– Synchro monsters

Source:
https://www.yugioh-card.com/japan/topics/?20131122