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University of Illinois Extension

Gray Mold [Annuals and Herbaceous Perennials]

Botrytis cinerea & paeoniae 


5 (1 = rare 5 = annual)  


5 (1 = very little damage 5 = plants killed)  


Affects many herbaceous plants including: Achillea sp. (yarrow); Chrysanthemum sp. (shasta daisies and mums); Echinacea sp. (coneflower); Heuchera sp. (coral bells); Paeona sp. (peony); Rosa sp. (rose); Tulipa sp. (tulip); and a wide range of other plants.    


Botrytis (known as gray mold; on tulips it is known as tulip fire.) appears as brown dead areas and under proper moisture may have a gray fuzzy appearance. The pathogen attacks buds, flowers, flower buds, leaves, leaf buds, and stems. It may eventually kill the perennial.  

Life Cycle

This pathogen over-winters on dead and live plant material. It grows at temperatures between 32 and 84 F. Botrytis releases spores on rapidly rising and lowering humidity. It needs free standing moisture to infect.  


Fungicides and sanitation may be helpful.

Filed under plants: Flowers

Filed under problems: Fungal Disease

More information is available on Hort Answers.