In episode 37 "Ging × And × Gon" we can see that a tape was left for Gon by his father Ging. After playing this tape, the scene jumps to Ging riding atop two different beasts. The scene clearly shows a giant tree in the background.
Now, this tree size is substantially larger than anything else seen in the series except for the World Tree that Gon climbs up in episode 148 "Until Now x and x From Now". The tree showed in the scene looks to be even larger than the adolescent world tree. Ging also states that he has not been to the Dark Continent yet due to him meeting not meeting the requirements.
Would it be safe to assume that there was more than one World Tree seed that found its way to the "known" world?