Parsley is often used as a garnish. “If a parsley farmer is sued, can they garnish his wages?” is a pun that has been printed on many images.
 
American comedian Bruce Baum said in July 1990, “If a parsley farmer goes bankrupt, can we garnish his wages?” Baum was quoted in the Los Angeles (CA) Times on December 1, 1990, “If a parsley farmer goes bankrupt, can the IRS garnish his wages?”
 
American comedian George Carlin (1937-2008) is sometimes credited, but he is not responsible for the one-line saying.
   
       
Wikipedia: Parsley
Parsley or garden parsley (Petroselinum crispum) is a species of flowering plant in the family Apiaceae, native to the central Mediterranean region (southern Italy, Greece, Portugal, Spain, Malta, Morocco, Algeria, and Tunisia), naturalized elsewhere in Europe, and widely cultivated as a herb, a spice, and a vegetable.
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Parsley is widely used in European, Middle Eastern, and American cooking. Curly leaf parsley is often used as a garnish.
 
Wikipedia: Bruce Baum
Bruce Baum is an American comedian. His live act consists of prop comedy as well as more traditional stand-up material. One of his best-known stand-up routines is his diaper-wearing Babyman character. Baum is recognized for his large mustache and long hair and is often described as a David Crosby look-alike. Baum and comedian Barry Marder co-authored the Letters From a Nut series of books, written under the pseudonym Ted L. Nancy.
       
28 July 1990, The Times (Trenton, NJ), “Good Humor,” pg. B1, col. 1:
“If a parsley farmer goes bankrupt, asks Bruce Baum, “can we garnish his wages?”
   
1 December 1990, Los Angeles (CA) Times, “Comedy Review: Duo Deliver Frantic Pace, Double Punch Stage: The pairing of Debbie Tate, followed by headliner Bruce (Babyman) Baum proved to be a perfect match” by Glenn Doggrell, San Diego County Edition, pg. F5, col. 1: 
Someone must have known what they were doing when they set Debbie Tate up with headliner Bruce (Babyman) Baum this week at the Comedy Nite in Oceanside.
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The glue for Baum’s rambling act is high energy, the props and silliness (“If a parsley farmer goes bankrupt, can the IRS garnish his wages?”) as he bounces through his material with little or no regard for where he’s going.
   
22 February 1997, The Post and Courier (Charleston, SC), “Your office reveals a lot about you” by Elsa McDowell, pg. 1:
By the way, when a parsley farmer is sued, can they garnish his wages?
   
Google Books
A Treasury of Humor:
Thousands of humorous stories, jokes, anecdotes and one-liners, up-to-date and categorized for ease of use
By Lowell D. Streiker
Peabody, MA: Hendrickson
2000
Pg. 292:
If a parsley farmer is sued, can they garnish his wages?
 
Twitter
Marti Lawrence‏
@Marti_L
Replying to @conniereece
@conniereece - If a parsley farmer is sued, can they garnish his wages?
10:10 PM - 29 Jul 2007
   
Google Books
Ifferisms:
An Anthology of Aphorisms That Begin with the Word “IF”
By Dr. Mardy Grothe
New York, NY: Harper Collins
2009
Pg. ?:
If a parsley farmer is sued, can they garnish his wages?
       
Twitter
Bill Hurlbut‏
@BillHurlbut
If a parsley farmer is sued, can they garnish his wages? -  George Carlin
7:37 AM - 6 Apr 2009
 
Google Books
Chuckle, Giggle, Snort!: Quips
Collected By Karen Money Williams
Lulu Press (Lulu.com)
2013
Pg. ?:
If a parsley farmer is sued, can they garnish his wages?
 
Reddit—Oneliners
If a parsley farmer gets sued, can they garnish his wages?
submitted December 6, 2017 by Kas585