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Hi, Mig, Your dahlia could be

Hi, Mig, Your dahlia could be in shock so give it a little time. Ideally the soil in the "new" pot is a combination of sterilzed potting soil (you don't want to contribute pest or problems to the mix), peat moss, and perlite. And you have set the tuber 1 to 2 inches deep, horizontally in the pot. And the tuber is not soaking wet. And it should get sun.

Hope this helps—