You can eat them raw in salad or bake in bread.
It is not known if all dahlias are edible but dahlia pinnata are.
http://www.eattheweeds.com/dahlia-pinnata/
Seems that some species of dahlia tubers are edible and other are toxic if eaten in large quantities.
Dahlia tubers can be stored in a heated garage, crawl space or basement. Or you can choose to just buy new tubers each year.
Dahlia store food in their tubers.
They are called tubers.
You can buy them at garden centers, on the internet, or at Dahlia Society plant sales.
Seems that some species of dahlia tubers are edible and other are toxic if eaten in large quantities.
Dahlia flowers will create seeds. You can also split the tubers or create more dahlias from cuttings.
You can buy them from flower catalogs, online gardening stores, local gardening stores, and from the Dahlia Society.
You need to store the tubers in a dry room that is about 50 degrees Fahrenheit. This is usually a heated garage or basement.
Aztecs used to eat the tubers. Now we just enjoy the flowers.
After the first killing frost, you cut the foliage off the dahlia and dig up the tubers. Bring the tubers indoors and store them at about 50 degrees Fahrenheit.
You need to dig the tubers four to eight days after a freeze.