Start tubers in flats or pots. Remember what you buy from the mass merchandiser will most likely be Dutch pot roots. Do not be dismayed by the tuber loss. Most of these broken/loose tubers are just those that grow out of the main tubers. If you have time and want to, you should be able to take several cuttings for additional plants. Otherwise just plant the pot root in a 6-8″ pot with good potting soil. Planting in pots gives the dahlias a real good head start and assures you that they are viable before they are planted out.
When planted in borders be sure the ground is enriched with compost and the soil is well worked. Perhaps add approximately a coffee can full of dehydrated cow manure or worm castings to the area before you work the soil. You will want to pinch the the terminal bud to encourage a fuller plant. You can do this when the plant is still in the pot. Then make a second stop after the plants have been in the ground a few weeks. This double stopping assures a really full plant with lots of blooms. For the rest of the year, you need not pay much attention to the plants. About the middle of July, though, a liquid fertilizer spray will be helpful.
Good mulch will pay dividends for the effort. The mulch will keep the weeds down and retain moisture. This is beneficial not only to the dahlias but also the other plants. Keep an eye out for the critters and be sure the dahlias get lots of water once they really start growing. Like most other flowers, removing spent blooms encourages new growth and more flowers. Disbudding is not necessary and some varieties do well without this step. Others will reward you well for the effort. Digging and storing after a killing frost is a matter of choice. If left in the ground there is the strong chance they will be frozen and lost. If this happens they will have to be replaced the next season. With the low cost of replacement this loss is not a major thing. If you do decide to dig just treat the clump as any other dahlia.
This same size dahlia is very much at home in a container. The big advantage of growing in a container is the portability of the container. Container gardening opens a whole new world for the gardener. Many excellent books are available for growing container dahlias. In fact, there are more books on growing in containers than most other horticultural subject. if container gardening piques your interest, stop in your garden center for help.
Depending on the size of your container you can enjoy combining other plant material to enhance the whole effect. Try combining with foliage plants and those plants with complimentary colored flowers. So why not try some dahlias in your favorite container? You will surely be thrilled with the results.
Include dahlias in your garden plans. You will not regret growing the dahlia, which blooms early and continues until frost.