Dahlias grow in most any well drained soil. As for exposure, full sun is the best, however they will tolerate some later afternoon shade. Plant after your last frost, usually Mid May in Minnesota. Making sure the soil temp is above 55 degrees. Apply a good comopost or balanced fertilizer to the soil but avoil high nitroen fertilizers. Lay tuber flat in a hole about 4" deep and cover with soil. We do not water our tubers until we see them starting to sprout above the soil to prevent tuber rot. Once they begin to sprout, we start watering weekly. Once they are blooming we water every couple days. We apply fish emulsion to our tubers one time every 4 weeks thru the summer to keep blooming as prolific as they can. 

All Dahlia varieties grow a little different, but generally spacing around 2' apart is sufficient. A good stake or tomato cage works well to keep the plants supported. Dahlias will grow 1' tall to 5' tall in one growing season. The average is 3-5' tall. 

After the first frost in the fall it is time to dig up your dahlia tuber clumps. Dahlia tubers will NOT survive if they freeze. So they must be lifted in MN or other northern climates. You can divide then in spring or fall. Dividing takes practice and patience. But it will gift you with 5-10 tubers per clump in one season! Each new tuber must have an eye for growth next spring. Wash soil off, divide tubers, allow to dry for a short time, bag with vermiculite and then store in a cool place that will NOT freeze.