“Give a weed an inch and it will take a yard” (or “If you give a weed an inch, it will take a yard”) is a jocular saying that has been printed on many images. This is a variation on the old saying, “give someone an inch and they’ll take a yard/mile.”
     
“If you give a weed an inch/ It will take a yard” was printed in the Drumright (OK) Derrick on June 24, 1947. “Give a Weed An Inch and it will take your yard” was printed in the Tacoma (WA) News Tribune on June 25, 1947. “If you give a weed an inch it takes a yard” was printed in the Tooele County Chronicle (Tooele, UT) on June 27, 1947. “If you give a Weed an inch, it will take a yard” was printed in the Kossuth County Advance (Algona, IA) on July 8, 1947. “Give a weed an inch and it will take a yard” was printed in The Spokesman-Review (Spokane, WA) on August 30, 1956.
 
   
Wiktionary: give them an inch and they’ll take a mile
Alternative forms
. give them an inch and they’ll take an ell
. give someone an inch and someone will take a mile
. give someone an inch and he’ll take a yard
Proverb
give them an inch and they’ll take a mile
1. Granting someone a limited concession will encourage them to take greater liberties.
       
Newspapers.com
24 June 1947, Drumright (OK) Derrick, pg. 3, col. 3 ad:
If you give a weed an inch
It will take a yard.
(Leland C. Seay, insurance.—ed.)
 
Newspapers.com
25 June 1947, Tacoma (WA) News Tribune, pg. 3, col. 1 ad:
Give a Weed
An Inch
and it will take
your yard
(Braley’s druggists.—ed.)
 
Newspapers.com
27 June 1947, Tooele County Chronicle (Tooele, UT), pg. 8, col. 2:
If you give a weed an inch it takes a yard.
 
Newspapers.com
8 July 1947, Kossuth County Advance (Algona, IA), pg. 6, col. 6 ad:
“If you give a Weed an inch, it will take a yard”
(...)
KOSSUTH CO. WEED COMMISSION
 
Newspapers.com
28 February 1950, Calgary (Alberta) Herald, “The Scrap Book” by Beverly Gray, pg. 4, col. 3:
If you give a weed an inch, it takes a yard.
   
Newspapers.com
7 July 1952, The Daily Sentinel-Tribune (Bowling Green, OH), “Noah Numbskull” comic strip, pg. 2, col. 2:
DEAR HOAH—IF YOU GIVE A WEED AN INCH, WILL IT TAKE A YARD?
 
Newspapers.com
30 August 1956, The Spokesman-Review (Spokane, WA), “Shop with Sue,” pg. 8, col. 8 ad:
Give a weed an inch and it will take a yard.
 
Google Books
Hiking the Appalachian Trail - Volume 2
By James R. Hare
Emmaus, PA: Rodale Press
1975
Pg. 1251
Others are “It takes a lean horse for a long race,” “Give a weed an inch and it will take a yard,” “Every cow needs a tail in fly time,” “It’s a poor dog that won’t wag his own tail.” and “Fine as fur in the North.”
   
Twitter
GreenWise®
@GreenWiseLiving
@BHGGarden @Garden_Organic @GardeningAus @BHG
@ABCGardenExpo “Give a weed an inch and it’ll take a yard”
6:27 AM · Mar 16, 2011
   
Twitter
Jenny Clifton
@estrojen1193
Aug 14 - Give. “Give a weed an inch and it’ll take a yard.”—Mom wisdom
#fmsphotoaday #vscocam
10:19 PM · Aug 14, 2014
 
Google Books
Give a Weed An Inch and It Will Take a Yard
Gardening and Plant Records and Scheduling Notebook, Track Your Plants Name, Date Planted, Water and Sunlight Requirements
By Goldrush Publishing · 2019
     
Twitter
LawnCrafters
@LawnCrafters123
If you give a weed an inch, it’ll take your yard! 🤣 📏
Our #organic-based treatments target common weeds:
🍀 Clover
🦀 Crabgrass
🦊 Foxtail
WEED hate to see weeds take over your lawn! 😉 If you’re in or around #MankatoMN, call today! 507-414-8387
https://katolawncare.com/weed-control/
10:06 AM · Nov 22, 2022
 
Facebook
Indian Hills Community Sign
April 23, 2023 at 2:05 PM ·
(The following text is shown on a sign.—ed.)
GIVE A WEED
AN INCH
AND IT WILL
TAKE A YARD