Interesting concept.
I played a few rounds and got a high score of 17. In the end, my score really depended on how closely the RNG placed bushes together. Sometimes I could get 5 or 6 in one explosion, and other times I was lucky to get 3. In the game that I got 17 I didn't need to harvest my corpses at all.
I think a much bigger map is one way you could improve this. That would make the mechanic of harvesting your corpses for time a bit more important, because then you would need the extra time to take long trips to find distant areas with lots of close bushes. And maybe some upgrades that you could collect to change the way your explosion works, so that your score could be dependent on a little more than RNG bush placement.