Posted: 26/02/2014 at 23:18
Dahlias are one of the most promiscuous of cross-pollinators and you never really know what you will get from seed saved from ones grown in your garden. The clue is probably in the name: "variabilis"! There are literally thousands of scientific papers on the subject of their genetics.
Best thing to do is to sow lots then wait for them to flower and remove those you don't like. If you get one or two you really like and want to multiply, then lift the tubers over winter, start them off in a deep tray the next spring and keep cutting and propagating the new shoots, all of which will grow into identical plants to the 'mother' tuber.