Bloom Man Group

At the top of every hour for the Superbloom event in the Emerald Dream zone (indicated by the horn icon on the map), Sprucecrown spawns two (2) seeds which allows you to choose powers from, each seed letting you pick one of two choices. It will be seemingly RNG with "Feral Overflow" to be an option to select.

If you do choose Feral Overflow, start participating and begin doing objectives/killing mobs tied to the Superbloom event to gain +Bloom. There will be a buff you can track that has a stack counter that goes up to 200 before it resets. It might be seemingly buggy but upon it reaching 200, it spawns a mob during the escort event and normally would grant +1 credit toward the achievement.

During the last two (2) stages of the Superbloom event, you will continue to gain stacks for the Feral Overflow buff gaining +bloom but it will no longer spawn the mobs, so you won't be able to gain easy spawn credit during the most mob density stages.

Hit 200 twice-no idea if anything spawned-was in a raid group-zero credit towards achievement

Make sure you aren't in a raid if you are going for this achievement as it won't count