I purchased a plant a while ago and left it in the pot. After about 10 days, it got powdery mildew on the leaves. I sprayed it with milk/ water solution which helped, and cut off all the affected leaves. There is still the odd leaf that is coming up with some mildew showing. I will spray it again. Is the plant safe to plant in the ground, or will it affect the area? The plant is a brown-eyed Susan
type plant ( sunflower ?) Thank you.
There are native Brown-eyed or Black-eyed Susans (Rudbeckia hirta) and many varietals: R. fulgida ‘Goldsturm’ has been a favourite for many years. The former produces prodigious amounts of seed and freely seeds itself in the wild or garden. It is tall, and has many small daisy-shaped flowers with yellow petals and a brown or black ‘eye’ (seeds). The latter, and many other cultivars, have been bred to be shorter, but with much larger, sometimes differently coloured, daisy-shaped flowers. These don’t seed quite as freely as the native flower.
What you probably have is a varietal, that is often found in late summer, brought into local and larger garden centres. They are in full bloom, ready to enhance your garden that is winding down for the fall. At the same time, many ornamental grasses, kale, and mums are ready to do the same.
The Rudbeckia family are susceptible to powdery mildew. They often grow crowded together, along with the blooming asters at this time of the year, and the poor air circulation, warm weather, more frequent rains, encourage the growth of this fungus. Although not familiar with the milk and water method, some anti-fungal sprays do work. Keeping the area diligently clean of affected leaves keeps the fungus from forming, but there are no guarantees.
In your case, I would not plant it in the garden, as it will, even with diligence, introduce the fungus to your garden. Enjoy the pot of flowers for the season and toss it when done. But before you do, you can harvest the ripened seeds from the ‘eye’, if the birds haven’t already eaten them. Finches are particularly fond of the seeds and will perch on the ‘eye’ and eat the seeds. You can scatter the seeds now, or wait until spring. Either way, you will have rosettes of new plants in the spring and wonder where they all came from.