City officials in Henderson, Nev., recently questioned a licensed marijuana grower about his relationship with President Donald Trump’s personal lawyer, Michael Cohen, according to documents viewed by The Wall Street Journal and the grower himself.

The marijuana grower, Semyon “Sam” Shtayner denied to the city officials that Mr. Cohen had any involvement in his pot business. Rather, he said, Mr. Cohen and his family had lent him money in the past to finance taxi medallions.

Mr....