In both Britain & her American colonies, women & men often worked side-by-side to gather the hay. Of course, the danger with having men & women working together is clear from the couple taking a break in the background enjoying each other in the shelter & shade of the haystack.
Origin - This proverb is first recorded in John Heywood's "All the Prouerbes in the Englishe Tongue" 1546:
Whan the sunne shinth make hay. Whiche is to say.
Take time whan time cometh, lest time steale away.
Many proverbs exist in other languages, but this one doesn't, and it's a reasonable surmise that the phrase is of English Tudor origin.