Hi Cynthia,

Thank you for contacting the UNH Extension Yard and Garden Infoline with your questions about donating your Rubeckia plants to your garden club plant sale and about how to control powdery mildew on your Joe Pye Weed plants.

I have included a link to a fact sheet that provides guidance about how to end the gardening season.  It recommends, "DO remove potential sources of disease for next season. Remove plant parts with powdery mildew, black spot, early blight, etc. Don’t compost them, as that can potentially spread disease problems further."

https://extension.unh.edu/blog/2023/10/closing-out-gardening-season

You can donate your Rudbeckia plants to your garden club plant sale as long as the plants are healthy and do not have black spot when you donate them.  Full sun can help prevent black spot.  I have included links to a few fact sheets that discuss how to grow Rudbeckia plants.

https://hgic.clemson.edu/factsheet/rudbeckia/

https://plants.ces.ncsu.edu/plants/rudbeckia-sullivantii-goldsturm/

https://extension.msstate.edu/publications/rudbeckia-for-the-mississippi-gardener

I have also included links to fact sheets that discuss how to control powdery mildew.

https://extension.umn.edu/plant-diseases/powdery-mildew-flower-garden

https://www.extension.purdue.edu/extmedia/bp/bp-5-w.pdf

https://homegarden.cahnr.uconn.edu/factsheets/powdery-mildew-on-ornamentals/

The following are links to fact sheets that discuss how to grow Joe Pye Weed.

https://hgic.clemson.edu/factsheet/joe-pye-weed/  This fact sheet includes a link to a fact sheet that also discusses how to control powdery mildew.

https://plants.ces.ncsu.edu/plants/eutrochium-purpureum/