Dahlia Flower Requirements. Dahlias that are particularly suited for use as cut flowers need to possess certain attributes that may or may not be essential to garden or show quality dahlias. Pots require more regular watering.
Add compost and all-purpose granular fertilizer to the planting area and mix well. Loosen the soil to a depth of 12. Pots require more regular watering.
Dahlia plants grow and bloom best in full sun.
2 3 inches above the top of the tuber. Dahlias are classified according to flower shape and petal arrangement. The fully double flowers up to 8 in. Sunny should include at least a couple of hours morning sun.