Matt Woodruff put the sign outside his business in Lewes for just six hours on Saturday but that was all it took for a picture to spread across the world on social media.
The “important notice” read: “Please could anyone who voted Conservative identify themselves on entering my shop as I will be happy to apply a 10 per cent ‘Tory tax’ on your plants.
“I'm sure, as someone who has opted to support a party of elitist, self-serving types, that you understand that this is one of the many ‘tough’ decisions that I need to make to ‘balance the books’ under your preferred government.
“Don't be a shy Tory! Oh, and Ukip voters, please shop elsewhere.”
Mr Woodruff, 46, told The Independent it was a light-hearted response to “dismay” in the East Sussex town after Liberal Democrat MP Norman Baker lost his seat to the Conservatives by little over 1,000 votes.
He has owned Woodruffs Yard for seven years and said he believed the vast majority of customers would agree with the sentiment.
“The support has been overwhelming,” Mr Woodruff added. “I've had hundreds of emails from everywhere from the Highlands to Cornwall, as well as Sweden and Australia.
“It’s resonated in a way that really shocked me because it was just a little blackboard.” Mr Woodruff said people in Lewes were 'dismayed' at Liberal Democrat MP Norman Baker losing his seat to the Tories
However, not everyone was impressed. The business has also been inundated with abusive and insulting emails and Mr Woodruff said his daughter became the target of “vile trolling” after she supported him on Twitter.
The response on the local Lewes Forum was mixed, with one person praising his “great sense of humour” and another planning to travel 200 miles to frequent the garden centre because of its “principled and witty proprietor”.
But one former patron claimed Mr Woodruff had lost their custom with the “blatant anti-Tory message”, adding: “If it was meant to be 'tongue in cheek' it has badly misfired.”
Even former English Defence League leader Tommy Robinson stepped into the online fray on Sunday, calling Mr Woodruff a “fascist”.
"He obviously doesn't get the irony," Mr Woodruff quipped.
The garden centre owner, who describes his political views as "broadly socialist", said people claiming to be Ukip supporters had threatened to smash up his shop.
“A lot of the nasty emails seem to have a fixation with male genitalia, it’s laughable really,” he added.
“One said he hoped my genitals would be eaten by slugs, so they get quite inventive.”
Mr Woodruff said he was unsure whether the sign, which is no longer on display, would affect custom as he was closed on Sunday as it went viral.
“I’m not really taxing anybody, it was just a joke - I’m glad it stirred things up,” he added.
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“I thought most people in the town would appreciate the irony and get the joke. I don’t want to discriminate against anyone, apart from Ukip voters.
“People can come in for a chat and a debate while buying their plants. It was a good way of getting people talking.”
Only one Conservative voter has come forward so far, resulting in a “laugh and a chat”, he said.
It is not the first time Mr Woodruff has aired his views using the blackboard, following a self-described “rant against multinationals” after a local Waitrose supermarket set up a plant stall.
He said: “I don’t do Facebook or Twitter or any of those things, I just write on the blackboard. We need more blackboards in the world - the chalk is mightier than the sword.”