A math riddle has been printed on several images:

*Q: What happened to the plant in math class?
A: It grew square roots.*

The “square roots” joke has been cited in print since at least 1961.

Google Books

*Arithmeriddles*

By Lowry Waring Harding

Columbus, OH: Association for the Study of Educology, Ohio State University

1961

Pg. 80:

Q. What happened to the plant in the classroom arithmetic corner?

A. It multiplied, divided, and grew square roots.

Google Books

May 1963,

*Boys’ Life*“Think and Grin,” pg. 82, col. 2:

Jim: Do you know what happened to the plant in the math room?

Jan: No, what?

Jim: It grew square roots. —

*Douglas Hansen, McKenzie Bridge, Ore.*

16 December 1966,

*News Journal*(Mansfield, OH), “Fun Time—The Chuckle Box” by A. Leokum, pg. 33, col. 7:

Bob: Do you know what happened to the plant in Math class?

Ted: No, what?

Bob: It grew square roots.

18 June 1967,

*The Sunday Sun*(Baltimore, MD), “Sunday Punch,” Magazine, pg. 26, col. 2:

AFTER the first semester the plant in the math teacher’s class grew square roots.

Google Books

*School Jokes For Kids*

By Peter Crumpton

PeteyRF Creative

2015

Pg. ?:

What happened to the plant in math class?

It grew square roots.

Reddit—Jokes

What happened to the plant in math class?

submitted February 17, 2015 by itsnotzack

It grew square roots.

Reddit—Jokes

What happened to the plant outside the math class window?

submitted January 8, 2016 by thegeneral400

It grew square roots.

TVOMathify

@TVOMathify

Q: What happened to the tree outside of the math class? A: It grew square roots! #mathjoke

4:00 PM - 17 Feb 2017

Reddit—Jokes

What happened to the plant in math class?

submitted July 12, 2018 by MNCPA

It grew square roots.