What kind of soil do dahlias like?

I think this dahlia would be best grown in rich, well-drained, and slightly acidic soil, which should give it the perfect environment for growth.

I think this plant would do best in a mixture of clay and sand soil.

I've read that some folks recommend a high-quality potting mix, along with some Leafgro (leaf mulch) and at least 20 to 25% (by dry matter) vermiculite or perlite.

You can plant it in a mixture of soil combined with compost, manure, and a bit of peat moss. That soil I mentioned should give your plants a nice planting medium with good drainage.