flower pots under douglas fir

Asked August 6, 2019, 2:28 PM EDT

Over the years I have planted petunias in pots & put them around a doug fir that grows up through my deck. Every year about this time they start to get a white, powdery look and small holes in the leaves and they quit blooming. Is there an insect in the doug fir that could be doing this? I see earwigs and potato/pill bugs. Would there be a better choice of flower for my deck pots next year? Thank you! Lynn

Clackamas County Oregon container gardening powdery mildew flowers: annuals and herbaceous perennials

1 Response

It is not a matter of which plants to plant under a fir tree since they are potted plants and not planted directly in the ground. It is more of an issue of following the specific plant’s care instructions. For example, petunias prefer full sun and will produce the most flowers if they get it. They can survive in partial sun as long as they get 5 to 6 hours of direct light every day. If your petunias are in the shade, that might be your problem for the lack of blooming.

Powdery mildew fungi attack petunias with a display of easy-to-recognize symptoms. When fungus attacks, powder-like spots of a mold-like substance forms on plant surfaces in addition to the formation of white fruiting bodies, or growths, that become black. Symptoms occur on leaves, stems and flowers. Appearing most prevalently in drier climates and warm temperatures as well as in damp, shaded conditions, powdery mildew is controllable through cultural management by watering your petunias early in the morning so water doesn’t sit on the leaves, avoiding overhead irrigation, and removing and destroying affected plant parts to prevent further spread of the fungus. Employ the use of a botanical fungicide like neem oil for lower toxicity. Make applications once every one to two weeks during the growing season.

Also for preventative measures do not reuse your potting soil and clean the pots. Please refer to this Iowa State University article.

Good luck and happy gardening.