To ensure that this functions as intended, there's one extra step you will need to do. Delete Radstorm Removal.esp that is added by Regrowth. What's the point of the pukeydoomland if there's no diarrheafartfog to accompany it?
Anyhow.
Required mod, of course, Regrowth Overhaul.
Recommended mods to accompany the pukeydoomland:
ReGrowth - Settlement Lawn Mowing
True Storms
If you get true storms, I recommend adding in anything that ups the radstorm shenanigans (less chance anywhere else, but up the difficulty of them regardless... endless fun in the glowing sea!)
I also recommend Deadlier Deathclaws.
And Super Mutant Redux.