Denom has been walking around lately looking quite pleased with himself thanks to the mysterious prosperity of the crops. Denom is the mechanic/gardener responsible for maintaining the wind turbine, condensers, and greenhouses. As for his success with the crops, he had a stroke of luck encountering a merchant selling special fertilizer.
Kill the weedlings: When the Prisoner first arrives at the Mesa Top he will find Denom and the Ciphers battling a group of weedlings in one of the greenhouses. Whether or not the Prisoner assists or not is up to him.
Figure out what Denom did to the crops: Azkee is worried about the crops. They're unnaturally large, and he's concerned that Denom might have done something to "improve" the fields which might ultimately prove detrimental to the Ciphers.