Trees with their roots and everything basically hold on to a section of land(dirt/stone/whatever) if one thinks about it.
A certain species of tree has fibrous roots and a poisonous, flexible, vine-like trunk that gets longer as the tree ages. It has evolved to form a giant hydrogen gas balloon, instead of branches and leaves, whose translucent membrane is filled with chlorophyll to make use of light bouncing around inside it, the hydrogen being produced from the water it takes in and expelling waste oxygen. The balloon eventually gets big enough to lead to the tree uprooting itself and popping somewhere high above due to the eventual too great pressure differentials and it is this way that it spreads its seeds via the wind carrying it somewhere else.
Since the balloon both carries the tree and rips it out of the ground it should provide enough buoyant lift to carry the tree and some extra that's possibly stuck to its roots. Animals have next to no use for them, with only the eventual seeds providing sustenance, so they tend to be left undisturbed until they pop. Their native biome does not experience hale or too strong storms so rain isn't an issue for a premature pop before the seeds are ready. I'm calling it a 'tree' because of the size of this flora, even if its features would not likely lead to it being classified as one.
Is it possible for a closely-grouped collection of these trees to uproot at the same, carrying more dirt along than they usually would due to their roots growing close together, and not going too high into the air where they would've popped but instead have become what one might call 'floating islands'?