I present to you all, a story in slides.
So, when I first encountered the giant world at the end of the belt, it had something like ~2- or 3- thousand seedlings on it. Trying to amass troops, I quickly realized I could only get 500 seeds onto an asteroid at once, before my game started (seemingly) glitching. (I had tried getting a boatload all onto the two closest rocks, but they wouldn't go when I told them to; I figured it out eventually.) Anyway, I determined I would need to attack from all four asteroids in range at once, with the maximum amount possible:
No such luck. Either there were too many seedlings to coordinate, or there's a cap on how many incoming seedlings an asteroid can have; the flow of troops was limited to a trickle, and The enemy resurged anew with 3000+ hungry interstellar wasps.
I eventually noticed that the last asteroid (the 'lasteroid,' if you will) sent out something like 30 or 50 seeds to each of the four planets in range at regular intervals, and while I was amassing troops, their population slowly declined. Here's what it ended up looking like:
It felt a little weird wiping them out when they had only a couple dudes left, but I didn't want another population explosion, and have to wait all over for them to decrease by attrition.
It did make me a little sad that you can't pack a whole unholy host of seedlings onto one little asteroid. If I left 499 on one rock, and tried to send another full host of 500 in, only about 91 of them made it.