I have a row of Peonies 5 are short and yellow rest are just fine what could...

Asked June 16, 2015, 12:04 PM EDT

I have a row of Peonies 5 are short and yellow rest are just fine what could be wrong?

Lincoln County South Dakota horticulture

1 Response

Peonies can be healthy, vigorous and disease-free if grown on a favorable site that includes full sun, good air circulation, adequate water, and good drainage. However, in a year with excessive rain or if planted on a less than ideal site, peonies may suffer from disease. With our wet spring it might be that they have root rot: it presents with stunted, yellowed, plants that wilt, and die. They may be infected with Fusarium, Rhizoctonia, or Thielaviopsis; all fungal diseases; if so you should remove infected plants. Below I have inserted information on peony disease management.

Managing Disease: Prevent and Protect

It is very difficult to stop any disease in the season it appears. Prevention through proper site selection, cultural management and good sanitation is by far the most important step in reducing the incidence and spread of disease. Cultural measures such as improving air circulation, watering midday and watering only at the base of the plant (don't get the leaves wet) will greatly reduce infection.

Sanitation--or removal of any spent flower blooms, infected buds, leaves and stems--is best done during a dry, calm time of the day. It is very important to clean your pruner by dipping in 10% bleach solution or by spraying it with 70% rubbing alcohol after cutting off diseased plant material and prior to pruning any healthy plants. Carefully dispose of any infected plant material. Do not discard this debris in your compost pile.

In the fall, cut any diseased plants back to the ground or just below the ground and dispose of the infected material. Add well-composted organic material as a light mulch in early fall to help add nutrients and improve the soil. This organic compost can be lightly worked into the top inch or two of soil.

Fungicides help protect plants from disease; however, they are not very effective at "curing" a problem once it has started. A fungicide can be applied to protect new shoots, leaves and buds from infection. For optimum results, apply early in the season, spraying to thoroughly cover all plant parts including the base of the plant. Carefully follow label directions. I hope this helps.