If it smells like fish in Denver, it might be from this blossoming tree

DENVER (KDVR) — The warm weather brings blossoming flowers that fill Denver with the smell of tulips, daffodils and sometimes rotting fish.

The smell is thanks to a flowering tree often sprouting white flowers this time of year in Denver.

Signs of spring: These flowers are the first to bloom in Denver

These stinky trees are called Callery pears, and they are often known for the unpleasant smell in the spring air around Denver.

While the smell doesn’t exactly bring to mind “spring flowers,” the trees aren’t meant to attract humans.

Why do Callery pears stink?

The Denver Botanic Gardens told FOX31 that portions of flowers, like the ones on the Callery pears, produce smells that best attract its pollinators.

Things that “smell bad” are a human perception. The trees actually smell good to some pollinators. Many insects, like wild bees and species of flies, are attracted to smells humans find unpleasant, said Panayoti Kelaidis with the Denver Botanic Gardens.

The flowering tree isn’t the only one to blame for the smell. Hawthorns have a similar smell which attracts the same pollinators.

“When it comes to smell, portions of the flowers have evolved the capacity to create volatile compounds (usually oils) that evaporate in air or sunshine to produce the smells that best attract their optimal pollinators,” said Kelaidis. “These compounds can be ‘good’ smelling to humans (think roses or gardenias) or repugnant like most Aroids or pear trees.”

Callery pears invade the states

These smelly trees are considered an invasive species in many states, although they’re not so bad in Colorado.

The Callery pear species was transferred to America a century ago in an attempt to save destroyed pear orchards. Since then, the tree has expanded to over 30 states – including Colorado.

When will the tulips bloom at the Denver Botanic Gardens?

The trees have been described as an invader “worse than murder hornets.” But the trees aren’t necessarily invasive in every state.

Callery pears are extremely invasive in maritime climates, which usually get more than 30 inches of precipitation a year, according to Kelaidis.

“In wet climates, the seed germinates prolifically and grows quickly. They have become a nasty pest, although they are still being sold where they shouldn’t be,” said Kelaidis.

However, the seeds do not appear to either germinate, or don’t continue to grow if they do, in drier climates.

“They are a useful and worthwhile small tree for our regional landscapes,” said Kelaidis. “They are sold by almost every garden center.”

Get used to the smell of spring in Denver, even if that means passing by a smelly tree. While the trees aren’t meant for humans, they’re not going anywhere.

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