When you have Dust Knight, you can't risk using Botanical girl, a plant searcher that misses timing, just like Machina Peacekeeper and Pinch Hopper
All you really need is Dust Knight, Tribute to the Doomed, and Rose Lover
Also, this deck is missing DNA Surgery
An obvious +1 to +2 you can get with fragrance storm
Lord Poison is part of Yami Marik Torture deck in the real life yugioh.
The main combo play Lord Poison does is with Mystic Tomato.
Mystic Tomato is a plant which can help bring out dark monsters.
Basically, It helps bring out the monsters in Yami Marik deck.
The Lonefire Blossom + Gigaplant really don't need Lord Poison as an engine.