There are regular onions, and then there are onions too sexy for Facebook, a Canadian seed and garden supply store recently discovered.

The Seed Company by EW Gaze, in St John's, Newfoundland, had wanted to post a seemingly innocent advert for Walla Walla onion seeds on Facebook.

But to their surprise, it was rejected for being "overtly sexual".

In a statement on Wednesday, the social media company apologised for the error made by its automated technology.

The ad flagged by Facebook showed Walla Walla onions, known for their size and sweet flavour, piled in a wicker basket with some sliced onion on the side.

It took store manager Jackson McLean a moment to realise what the issue was with the posting, he said.

Then he figured out that "something about the round shapes" could be suggestive of breasts or buttocks.

He knew his customers would find the ad rejection funny, and posted the photo, along with the automated Facebook message warning "listings may not position products or services in a sexually suggestive manner", to the company page.

Mr McLean said some clients have been posting images of potentially suggestive carrots and pumpkins in reply.

He also appealed the decision to Facebook.

"We use automated technology to keep nudity off our apps, but sometimes it doesn't know a Walla Walla onion from a, well, you know," Facebook Canada's head of communications, Meg Sinclair, told BBC.

"We restored the ad and are sorry for the business's trouble."

The company is in the process of digitising its whole inventory to make shopping online more accessible amid the coronavirus pandemic, Mr McLean said, and that included boosting some advertisements, like the onion one, on Facebook.

The Walla Walla onions, "an older onion variety", had recently brought back in stock by customer request, and are now selling fast due to their newfound notoriety, he said.

"We've sold more in the last three days than in the last five years," said Mr McLean, adding they are also now listed under "sexy onions" on the company website.