Peonies in the University of Michigan’s Nichols Arboretum had a wee bit of help blooming this year after environmental engineering professors showered them in and unlikely fertilizer — human urine!

Researchers and professors Nancy Love and Krista Wigginton are passionate about pee, especially when it comes to peonies.

After receiving a $3 million National Science Foundation grant in 2016, the duo began testing advanced treatment methods and spreading the word about the environmental and economic benefits of utilizing urine as a fertilizer at the Nichols Arboretum’s show-stopping heirloom peony garden.

Nichols Arboretum Peony Festival.

Peony Festival at Nichols Arboretum. Credit: Santosdo via Wikimedia Commons (CC BY-SA 3.0)

The Arboretum makes for a beautiful landscape to demonstrate the power of pee fertilizer! Containing over 270 American, Canadian, and European 19th- and 20th-century peony varieties, the Arboretum rounds out to about 800 peonies — nearly 10,000 flowers when in full bloom!

Pee for the Peonies

Like all good marketers, Love and Wigginton knew that the best way to garner attention for a cause is with a great catchphrase. The phrase began as “pee on the peonies.” They soon realized that their catchy slogan was being taken literally by some weak-bladdered whiz kids and changed it to the more accurate “pee FOR the peonies.”

The dynamic duo will be spending weekends in May and June hooking visitors with the slogan before reeling them in with the cold hard facts about the nutrient flows, efficiency, and sustainability of urine-derived fertilizers.

“In general, people think it’s funny at first, but then they understand why we’re doing it, and they support it,” said Wigginton of the public’s response thus far.

What’s So Special About Urine?

Many alternatives to chemical fertilizers can help your garden grow, including eggshells, wood ashes, pet hair, and even fish carcasses. Still, urine is the liquid gold of them all, as it contains nitrogen, potassium, and phosphorus that help crops thrive — and it is easily accessible.

Prior to the experiments at the Arboretum, Love co-authored a study detailing her findings that urine diversion and recycling, or “pee-cycling,” resulted in significant reductions in energy and greenhouse gas emissions.

Love is committed to the idea of a “circular economy of nutrients,” in which human urine is collected to create renewable fertilizers, contributing to environmental sustainability.

Power to the Pee-ple

Before you drop those drawers to cultivate a garden of your own, it’s important to note that urine must be treated to be effective.

Though the fertilizer currently being used at the University of Michigan hails from Vermont, a collection toilet bowl is being housed in an engineering building on campus.

The split bowl helps keep pathogens from crossing streams, sending solid waste to a treatment plant while urine flows to a holding tank. Once the pee piles up, it’s treated to dilute trace amounts of bacteria collected in the bladder and aged to eliminate DNA that can spread antibiotic-resistant infections.

When collection efforts came to a halt due to the university’s COVID-19–induced closure, the research team used the time to improve their process by upgrading their freeze concentrator and adding an energy-efficient pasteurizer to the operation.

Love and Wigginton hope to have local fertilizers available next year.

By Meghan Yani, contributor for


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