When this card is Normal Summoned: You can choose either 1 or 2, then excavate that many cards from the top of your Deck, send any excavated Plant-Type monsters to the Graveyard, also place the other cards on the bottom of your Deck in any order. If this card is excavated from the Deck and sent to the Graveyard by a card effect: You can target 1 monster on the field; destroy that target.
Sylvan monsters have effects that excavate and send plant monsters to the graveyard, and Komushroomo can excavate up to 5 cards. Magical Merchant can also work well since it excavates and sends to the graveyard, possibly more than Komushroomo but with a potential to be lower. Being able to excavate multiple cards can potentially turn a duel around if you manage to excavate multiple Komushroomo or Marshalleaf.
Rose Lover is a really good card to put in a plant deck since it allows you to special summon higher level monsters much easier. Raging Mad Plants is a quick-play type spell that can be used in the damage step. You get higher attack increase the more plant type monsters you have in your graveyard. Amarylease is similar to Rose Lover, except you still have to use your normal summon.
Not really, as the entire point of Sylvan does not match with what Black Rose Dragon does.
You'll want Sylvans to be excavated from the deck, not destroyed from the field.
And BRD's second effect does not help Sylvan either as you'll want to return them to the deck so you can reuse them. BRD banishes them instead.