Pee for the Peonies
Our UM team will be at the Nichols Arboretum peony garden, beds 24-27, on Saturday May 30 from 10 am - Noon and Sunday May 31, 2026 from 12:30-2. We will be available to discuss our work in urine recycling, which produces a collection of pasteurized, nutrient-rich, licensed fertilizer products.
Please consider taking our brief 2-minute survey about preferred fertilizer forms. Respondents can enter a raffle for a chance to win free gardening shears!
For those interested in urine recycling for their gardens, learn more from the Urine My Gardenprogram developed by the Rich Earth Institute. Import fewer virgin fertilizers; recycle more from your own household!
In 2021 and 2022, we applied a treated, sanitized urine-derived fertilizer (UDF) from Brattleboro, VT to peony beds 24 & 26 (control beds: 25 & 27). Nutrients were applied in accordance with soil tests. In 2023 we did not fertilize. In 2024, we fertilized with UDF from our urine separation system on U-M’s north campus and created a 0.2-0.4-0.4 NPK product. We applied to one of two peony pairs in all four beds (24, 25, 26, 27). In 2025, we continued by applying fertilizer to one of two peony pairs, but made a stronger NPK product with a ratio of 1.2-2.3-2.3. The changes in NPK ratio come about as we have upgraded our processing equipment and learned how to concentrate more efficiently. In 2026, we increased the UDF NPK strength further to 3-4-5.
While the fertilizer needs of peonies are modest, our primary goal is to focus on how nutrients flow through our community, regenerative food-nutrient cycles, and how urine recycling can contribute to a more sustainable future.
“Pee for the Peonies” is a partnership between University of Michigan researchers in the department of Civil and Environmental Engineering and the Matthaei Botanical Gardens and Nichols Arboretum.
Kristina Bonnet applies U-M’s sanitized urine-derived fertilizer (UDF) to sprouting peonies in April 2025.
Fertilizing the Peonies
The 2026 peony fertilizing team
We fertilized on April 20, 2026 when most peony shoots were 12 to 18 inches high.
Water (2 left containers) and concentrated UDF (right container) are carried into the garden. We dilute the concentrated UDF to the desired ratio, then apply by pouring around each plant’s dripline.
Professors Rachel O’Brien (left) and Nancy Love (right) combine water and UDF concentrate to make solutions to apply to the peonies in 2025.
