Every site I have with info on these palms doesn't mention fertilizing.
I did a google with the term:
fertilize Bismarck palm and got over 28,000 hits.* There's lots of info to choose from.* :)*
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.