I have 5 peonies planted in full sun in my garden. For 6 years, they have...

Asked May 29, 2015, 2:41 PM EDT

I have 5 peonies planted in full sun in my garden. For 6 years, they have bloomed gloriously each spring. This year 2 of the 5 have grown up much smaller than before--fewer stalks, less height. No signs of blight or other defects in the leaves or flowers. What might cause this small size? Should I be concerned that there is a virus or other troublemaker that might spread to the other peonies? Should I remove the stunted ones?

Hennepin County Minnesota

1 Response

If the plants are stunted and yellow then check the roots for the small galls of nematodes or root rot. Diseased plants should be removed and destroyed. If the roots leaves and roots are healthy then check the growing conditions. Herbaceous peonies need at least six hours of full sun a day for good bloom. Well-drained, loamy soil is best for good growth of peonies. Good drainage is vital to avoid root rot and fungal diseases. If your soil is heavy clay, amend it with compost to improve the organic matter content. Apply a low nitrogen complete fertilizer such as 5-10-5 or 5-10-10 at the rate of two to three pounds per 100 square feet.

http://extension.psu.edu/pests/plant-diseases/all-fact-sheets/peony-diseases