“What do you get when you cross poison ivy with a four-leaf clover?”/“A rash of good luck.”

A four-leaf clover joke that has been popular on St. Patrick’s Day has been printed on several images:
 
Q: What do you get when you cross poison ivy with a four-leaf clover?
A: A rash of good luck.
 
The joke— originally involving a botanist— has been cited in print since at least 1976.
 
 
23 April 1976, Washington (DC) Post, “The District Line” by Bill Gold, pg. B18, col. 2:
Richard Barkey wants to know whether you’ve heard about the botanist who crossed poison ivy with a four-leaf clover and came up with a rash of good luck.
 
11 June 1976, Pittsburgh (PA) Post-Gazette, pg. 25, col. 4 ad:
TOM DICK, A LONG-TIME FRIEND OF THE PETROLIAS FAMILY’S SMITHFIELD CAFE (EVEN BEFORE CO-OWNER JIM PETROLIAS’ GEOPOLITICO SON, JOHN, WAS BORN) TELLS THE ONE ABOUT THE BOTANIST WHO CROSSED POISON IVY WITH A 4-LEAF CLOVER AND GOT A RASH OF GOOD LUCK.
 
22 July 1976, Centre Daily Times (State College, PA), “Good Evening!,” pg. 1, col. 5:
SCIENTIFIC: A botanist crossed poison ivy with a four-leaf clover, Sales Points reports, and came up with a rash of good luck.
   
Google Books
November 1976, Boys’ Life, “Think & Grin,” pg. 82, col. 2:
Tenderfoot: What do you get when you mix poison ivy with a four-leaf clover?
Eagle: A rash of good luck! — Bill Eckert, Knoxville, Tenn.
 
DISboards.com
Goofy’s….Galway Groans?....
Discussion in ‘Community Board’ started by Goofyposter, Mar 17, 2003.
(...)
What do you get if you cross poison ivy with a four-leaf clover?
........A rash of good luck!
 

Twitter
Tali McGregor‏
@TornadoAli
asks If you cross a 4 leaf clover with poison ivy, will you have a rash of good luck?? - Michelle
3:14 PM - 28 Aug 2008
 
Twitter
Jennifer Hynes‏
@ErkNJrk
What do you get when you cross poison ivy with a 4-leaf clover?
A rash of good luck.
10:22 AM - 28 Jan 2009
 
Google Books
A Man Walks Into a Bar 3
By Jonathan Swan
London: Ebury Press
2010
Pg. 274:
What do you get if you cross a four-leaf clover with poison ivy? A rash of good luck.
 
Google Books
The Mammoth Book of Really Silly Jokes
Edited by Geoff Tibballs
London: Constable & Robinson Ltd
2011
Pg. 481:
What do you get if you cross poison ivy with four-leaf clover?
A rash of good luck.
 
Google Books
Teacher’s Joke and Story Book
Collected by Stanley Graham
Bloomington, IN: AuthorHouse
2016
Pg. ?:
Q. What do you get when you cross poison ivy with a shamrock (4 leaf clover)?
A. A rash of good luck.