Peonies not blooming

Asked June 17, 2016, 5:22 PM EDT

Plants are probably 6 to 8 years old and bloomed profusely for many years. Then 3 years ago, stopped blooming altogether. No buds. Plants are healthy but not as lush or as tall as years before. Husband used preen on them 3 years ago. Could that stop them from blooming forever?

Becker County Minnesota

1 Response

Thank you for the question. There are many different formulations of the pre-emergent herbicide Preen. This product works to kill weeds after they germinate but before they emerge from the soil. The only way to know for sure if it is recommended for use on weeds around peonies is to read the label of your product. We don't know if it can interfere with blooming once the plant is growing well. You might wish to call the company and ask that specific question.

The Preen product your husband used did not prevent your peony from growing so it's logical to think of other reasons for failure to bloom. Peonies prefer all day sun and space between them and other plants. Is it possible that over the last 6-8 years, other plants or trees grew larger and reduced the amount of sun the plant gets? Has a new structure created shade? Have other plants started to crowd them out? If the plants were divided or transplanted and the eyes planted too deep, they may not bloom for a number of years. Thoroughly scout your plants for disease because this can result in failure to bloom as well.

Read about growing peonies from our North Dakota neighbors: https://www.ag.ndsu.edu/pubs/plantsci/landscap/h281.pdf

Thank you for contacting Extension.