“Why should you never iron a 4-leaf clover?”/“You shouldn’t press your luck.”

A popular St. Patrick’s Day joke is:
 
Q: Why should you never iron a 4-leaf clover?
A: You don’t want to press your luck.
 
The joke has been printed on many images and has been cited in print since 1978.
 
   
Wikipedia: Four-leaf clover
The four-leaf clover is a rare variation of the common three-leaved clover. According to tradition, such leaves bring good luck to their finders, especially if found accidentally. In addition, each leaf is believed to represent something: the first is for faith, the second is for hope, the third is for love, and the fourth is for luck.
 
Google News Archive
22 August 1978, The Free Lance-Star (Fredericksburg, VA), “Tell Me Why!” by A. Leokum, pg. 6, col. 2:
Why shouldn’t you iron a four-leaf clover?
You shouldn’t press your luck.
 
Google Books
October 1987, Boys’ Life, “Think & Grin,” pg. 65, col. 3:
Warped wise man says: “If you iron a four-leaf clover, you press your luck.”— Wayne Rich, Jefferson, Tex.
     
Google Groups: alt.teens.penpals
A Question I have about sex.
merry mcgrath
8/22/98
Laugh Lines from the tittillated:  1.  Why should you not iron a four leaf clover?  Because you don’t want to press your luck.
 
Google Groups: alt.2eggs.sausage.beans.tomatoes.2toast.largetea.cheerslove
GROANERS
Sînatra
5/22/00
(...)
Why should you never iron a 4-leaf clover? You don’t want to press your luck.
 
Google Books
More Really Silly Jokes
By Cyl Lee
Edina, MN: ABDO Publishing Company
2005
Pg. 14:
Why don’t you ever iron a four-leaf clover?
You might press your luck!
 
Google Books
The Everything Big Book of Jokes:
Hundreds of the Shortest, Longest, Silliest, Smartest, Most Hilarious Jokes You’ve Never Heard
By Evan C. Thomas
Avon, MA: Adams Media
2014
Pg. 105:
WHY IS IT ALWAYS A bad idea to iron a four-leaf clover?
Because you should never press your luck.
 
Irish Central
Top ten Irish jokes - a snippet of of Irish comedy
Jane Walsh @irishcentral March 07,2016 01:00 AM
(...)
4. Never iron a four leaf clover. You don’t want to press your luck.