Love this concept and the choice of using pixel graphics. Will there be a win condition? Or is it a score based game where the difficulty constantly increases until the player loses?

I think it would be a good idea to do some research into the current methods farmers use against invasive species as a flamethrower may detract from the message while you could instead find exciting game play using real world solutions

I like the idea of a tower defense-style shoot-em-up, but I worry that burning and attacking plants sort of goes against the "plant a seed" theme of this jam. Maybe it could be evil corporations or chemicals attacking the plants instead? The production plan could be fleshed out a little more too. Otherwise, I think the base concept can be great with a few tweaks, but the gameplay loop still seems engaging!

I would look at the game Atomicrops for both inspiration and ways to diversify. As it stands this is looking like a down-scaled version of Atomicrops and that game doesn't quite come off as a Serious Game so I hope that your narrative really pushes for your environmentalist impact.