The Rambam writes the following
הגדל בעציץ אע"פ שהוא נקוב והגדל בספינה אינו מביא ממנו כל עיקר שנאמר בארצם. אבל מביא מן הגדל בגג או בחורבה
— essentially saying that bicurim is not brought from something that grew in a pot, even if the pot had holes inside of it. Normally, I thought, we say a pot with holes is "yonek" (derives from the ground), and therefore we look at it as if it's part of the ground (in regards to trumos, maaseros, shvi'is). Why not also here? Is it because of the limud of "b'artzam" as the Rambam points out? Is perhaps my understanding of the halacha of a pot with holes in it not true or not according to all opinions (perhaps the Rambam disagrees)? When does the din of a "pot with holes" apply that we look at it as part of the ground and why not in this case?