I planted 2 trees at my house BEFORE i got the quest to do that exact thing!
How can I get rid of these trees so I can replant another 2 trees and get credit for a completed quest?
The other thing you can consider doing is talking to Briar or En or Blitz in the game. Ask if you can follow one of them when they go to poison a tree for planks and then you can follow behind to tend the plot and then plant your seasoned bean.