ANN ARBOR, Mich. — A pair of University of Michigan researchers are putting the “pee” in peony.

Rather, they’re putting pee ON peonies.

Environmental engineering professors Nancy Love and Krista Wigginton are regular visitors to the Ann Arbor school’s Nichols Arboretum, where they have been applying urine-based fertilizer to the heirloom peony beds ahead of the flowers’ annual spring bloom.