What is the difference in growth rate and number of blooms between the two ?

-none... More to the point is how many stalks are allowed to grow from the clump vs tuber. More stalks = more potential blooms. But most show growers reduce the number of stalks to get better quality blooms instead of quantity.

How does one plant a single tuber in a 4 to 6 inch pot ? Is there uneven root growth if I try to center the eye within the pot ?

-normally prestarted tubers in pots have the sprout to the side of the pot, with tubers laid down on their side under an inch or two of soil. No need to center the eye... The root growth will be fine.

Does a single tuber start slower than a clump since it has less tubers for root growth ?

- the variety type has more to do with starting time them tuber size. Many experienced growers keep the small tubers for themselves, as the plant puts down more feeder roots BECAUSE it doesn't have the safety net of excessive tuber starch to support it.

By the way, the purchased clumps in big stores are actually a pot tuber from a cutting the previous season, and the size of the resulting clump is restricted intentionally to keep shipping weight down. Often a store-bought 'clump' has many broken tubers with the eyes attached along the stem, but will still sprout and make full-sized clumps by fall.

Thanks !!

What is the difference in growth rate and number of blooms between the two ?

My Reply - I believe there is a difference in growth - from a clump you can get three, four or even ten shoots coming up from the ground. With that many (lets limit this to 5), every one of them sends out feeder roots - all looking for food in a small area - soon the food supply runs out and the growth rate (which should be continuous) slows down to almost nothing ... you get a lot of blooms on some varieties this way but they are usually smaller and the plant develops way too much foliage.

The dahlias I planted this year are all "clumps" purchased at a big box store or from an online retailer (not from a Dahlia farm). I am already thinking about buying from a Dahlia farm for next year since I had limited cultivar choices this year.

reply - There are lots of suppliers - check the American Dahlia Society web site for a list of such suppliers.

How does one plant a single tuber in a 4 to 6 inch pot ? Is there uneven root growth if I try to center the eye within the pot ?

reply - why use pots? why not some sort of container that will fit the tuber, as an example, I save containers that strawberries come in, plus you can purchase fiber pots that are 3 X 6 (roughly)

Does a single tuber start slower than a clump since it has less tubers for root growth ?

reply -you should know where root growth occurs on a planted tuber. It is not the end of the tuber, it is at the base of the new eye that emerges from a piece of the crown attached to the tuber. If you have a big tuber, the new plant will grow until all food from the tuber is exhausted and then it will start to send out feeder roots - this happens a lot hence plants that take a long time to recover from excessive heat and moisture loss - if you were to dig up the root, there would be no feeder roots - then when they did develop, they could be immature at the time of digging and not have enough strength to make it through winter storage. So next year, cut the tuber to fit your 4" pot, bury it completely and the feeder roots will start faster -

enjoy what you have planted this year.

Thanks Jim.