The Flowering Death is, without question, the most powerful enemy in the game - they have perfect defenses, 10,000 HP, and high attack power. Even at high levels, a single attack from the Flowering Death will likely hit the 999 damage cap, and they are essentially impervious to any kind of damage. Getting through the Greenhouse, which is required to reach Ruffleberg's Lab, requires the player to pass by rows of Flowering Deaths, several of which will attack as they pass and likely kill the player instantly.
The player is not intended to fight the Flowering Deaths. In Security Access, the player can deactivate the lights to the Greenhouse. With the lights off, the Flowering Deaths goes inert and the player can pass safely.
The player gets a measly 600 experience and 100 credits for killing a Flowering Death. Given the great difficulty in doing so, it is not worth the effort.