Canada's new polymer $20 bills have been rapped for melting and not working in vending machines.

Now, botanists say one of the maple leaves on the note shows a Norway maple, which is not native to Canada.

"It's rather sad. It's not the first time that it's happened," said Julian Starr, a botany professor at the University of Ottawa who specializes in plant identification and classification. "It's almost Canadian in the fact that we can't even get our symbols right."

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However, the Bank of Canada, which makes bank notes, says the $20 bill does not depict a Norway maple leaf, but rather a "stylized" design.

"We created an image for the bank note that represents a stylized Canadian maple leaf, if you will, so that it wouldn't represent any specific species, specifically not the Norway maple," said spokeswoman Julie Girard.

Ms. Girard said the bank worked with a botanist who specializes in trees. However, she declined to reveal the scientist's name, citing privacy reasons.

Prof. Starr, who has previously consulted for the Royal Canadian Mint, says there is no doubt that the leaf – which appears above the "20" – is from a Norway maple tree. It has five main lobes, or projections from the body of the leaf, and the tips are stringy. On the other hand, sugar maple leaves have just three lobes and the tips aren't stringy.

Norway maple trees, which are considered invasive in North America and have been banned in two states, are native to Europe and were introduced to North America in the mid-1800s. Canada has 10 native maple species.

As part of his classes, Prof. Starr chronicles a list of official botany errors, including on the penny and in the logos for the former Canadian Television Fund and the 2007 FIFA under-20 World Cup of soccer, which was held in Canada. The penny, he said, appears to show leaves from the plane tree rather than a maple tree. The coin's two leaves emerge from different parts of the stem, rather than being directly opposite each other, which is the case for maple trees.

Canada's polymer $20 banknotes were introduced in November.

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The bills don't work in thousands of vending machines and owners have complained that the Bank of Canada failed to listen to warnings about the amount of time it takes to reprogram the devices.

There have also been reports of polymer bills melting in the scorching summer sun.