Hi Michelephil and welcome to GoY. I'm sorry but without a photo we would be guessing in the dark, please take and add to your question.

If its too late to take a photo you might look up pompom dahlias on Google for starters? With more info about height, leaf shape, etc its pretty impossible to help as MG says.

That is one possibility but there are lot of others I can think of Stera.

Only too true MG!