A friend would like to use the phrase “Let a thousand flowers bloom” on a plaque, possibly with an attribution. She and I are aware that the phrase’s modern incarnation comes from the Hundred Flowers Campaign in Communist China in 1956-57, culminating in Chairman Mao Zedong’s invitation in Summer 1957 welcoming constructive criticism of the regime:
That invitation didn’t go so well for many of the intellectuals who took it seriously:
For the attribution on my friend’s plaque, I have been searching unsuccessfully for the original poetic source of the phrase. Can anyone point me to the poem from which Mao was drawing?
I think it was original, written by Mao or the Sam Seaborn of the regime for the purposes of the campaign. But I can’t find a cite to support that.
When the Wikipedia article says “the name of the movement originated in a poem”, I think it’s just clumsy wording. They are just noting that the 4 characters that are used to refer to the campaign are the first half of a longer 8 character poem - but a poem that was written as the slogan of the campaign, not a poem that predated it. (Of course, there are likely to be instances of just the two characters 百花 in earlier literature, but without the same connotation.)
As I say, though, I can’t find a cite - so if you need certainty please don’t rely on this. But I just wanted to note that the reason you can’t find the earlier literary reference is probably because it doesn’t exist.