Ah, so you do have a draft for this…(Posted in the thread about images a little while ago)
Ok, I definitely like the idea, but still a ways to go here. Some suggestions:
Despite weighing as much as a normal nut or bolt, these seeds are capable of riding on air currents much like the seeds of other trees.
I don't think you necessarily need this; appropriately enough, a lot of nut trees get by with seeds that just fall to the ground: Pecan trees, for instance. If you really want to get off the wall, crib off of nature: A lot of trees produce seeds with wings or shoot them off on a ballistic trajectory.
they do not practice photosynthesis
What if they did? The metabolism of your rusty metallic organism is almost certainly going to be electricity-based to begin with, and it's got all it needs to generate electricity: Corroding metal inherently generates a current (hence why batteries work), for starters. Solar panels are a min-maxed version of an effect that happens with all metal to some extent, and Thermoelectric generators work by generating current directly from the movement of heat through electrically conductive materials- say, from sun-heated leaves to the cool roots deep underground. It could also feed off of wireless signals: it's not going to recharge your phone, but if you have a big antenna, you can get a volt or so out of the air any place you can pick up a few clear radio stations.
On the story side, I think you can do a lot more with the discovery log. To clarify, I like the general idea of what you're doing with the origins (they're just a natural thing, insofar as an anomaly can be natural.) but you can do more with the idea that they gradually catch on that the things are alive. You might also tie in the fact that the Foundation was using this dump as a training site- Say, maybe this was a Foundation dump, where they send waste from their sites, including the stuff they incinerate, and these things just naturally spawned from that cocktail of mostly-neutralized residual weirdness. That makes it less of a coincidence than happening to find it in a random dump that they were using as a training site for some reason.