“Grow what you can and can what you grow” was a popular saying in 1942, during World War II, when food availability was limited. “Grow What You Can, Can What You Grow” was cited in a Canadian newspaper in July 1938. The saying is still used, although less often than in the 1940s.
 
 
12 July 1938, Winnipeg (Manitoba) Free Press, “Entries Heavy At Portage,” pg. 10, cols. 1-2:
In charge of S. M. Donaldson of Ottawa, was the Dominion department of agriculture exhibit where a bulletin exhorted farmers to “Grow What You Can, Can What You Grow,” and stressed the advantages of shelter belts on prairie farmlands and the value of vegetable cultivation.
 
15 May 1942, Hattiesburg (MS) American, pg. 12, col. 7 ad:
PLANT SEED And Plant Abundantly—Grow What You Can—Can What You Grow
(Barnes Seed & Feed Co.—ed.)
 
Google News Archive
17 July 1942, Calgary (Alberta) Herald, pg. 6, col. 3 photo caption:
“Grow What You Can and Can What You Grow”
 
Google News Archive
12 May 1943, The Evening Independent (St. Petersburg, FL), pg. 1, col. 4 classified ad:
“Grow What You Can
and
Can What You Grow.”
(Mason Jars for sale at Montgomery Ward—ed.)
 
CMU Online Digital Object Repository
21 June 1945, Saliine (MI) Observer, “Food Shortage Is Most Critical,” pg. 1, col. 1:
“Grow what you can and can what you grow” was the warning issued today by William Jakad, chairman of the Saline Victory Garden Committee as evidence mounted that the country is facing its most critical food shortage since the war began.
 
7 April 1974, Ada (OK) Sunday News, “Nan Wiley: Wilted Lettuce Dressing,” Food sec., pg. 8, col. 6:
With food prices as high as they are this is surely the year to grow what you can and can or freeze what you grow.
   
Google Books
Country Home
Volume 22, Issues 5-8
2000
Pg. 142:
Like the denizens of chat rooms today, they used nicknames such as Pond Lily and Lady Francis and signed off with slogans such as “24 hours from vine to brine” and “Grow what you can and can what you grow.”
 
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Nothing like growing an heirloom eggplant parm in your suburban backyard! Grow what you can, can you what grow! pic.twitter.com/RHC3mQJm
1:26 PM - 30 Sep 2012