That's not normal. Use a garden hose to spray them with water to see if it removes the residue. I commend you for starting your dahlias indoors. Mine are sleeping in the garage.

Thank you so much ctgardenguy for your advice. I could not find any good information as to what it was and how to handle it. Thanks also for your kind words about starting early. I'm sure your tubers will go full speed ahead as the weather gets warmer in Connecticut:).

I'm having the same problem with my dahlias I'm starting indoors. Anyone have any info on what is causing this and if I need to do anything to get rid of it?

Judy,

What kind of mix are you using in your pot? Is it soil from outside, by chance?

Is the white on your leaves clumpy like the original poster's images, or more like a powdery substance was dusted on the leaves?

Are your dahlias in a small space with moist, warm air, or are they in an open well-ventilated space?

Pictures would help, too.

-CiCi

I am using an organic potting mix that was stored outside. It starts out looking like a residue and then it clumps up. It rubs off fairly easily and it feels granular...like sand or salt. I cleaned up all the affected plants with a baking soda solution and that seems to have stopped it except for the one I moved outside and the white substance came back.

I also noticed the tips of some leaves turning soft and browning. Is this botrytis?