This site does present many different challenges to how one is usually introduced to how plants are handled in different areas of the U.S. and Canada.

You bought a dahlia tuber in June...in Dallas, Texas.

This plant is usually planted in northern zones....4, 5 & 6...in May....early and sometimes a bit later...right about the time our annuals are put out.

At this time, we expect the plant to produce something in the way of foliage that might take proportions of 2 or 3 or 4 feet wide.....about the same in height and produce many blooms which, because of the weight of the shoots, this plant has to be tied up or given some support.

Me, I arrange early on before the plant grows much, a criss-cross of thin cord (fishline works but can cut tender stems)
to which supports the plant and its neighbors well.

I'm surprise the store you bought the tuber from didn't offer some advice about how to plant and when to expect flowering.

I think I'll bow out and let one of your neighbors suggest what you should do at this late stage.

Normally, up here, we allow the foliage of our dahlias to be touched by the killing frost which turns the foliage black. Then the tubers are dug up and stored away in our basements (coldcellar) until next spring.

There is an alternative way of storing dahlia tubers in lieu of the usual putting them in boxes of peat moss/sand/vermiculite and keeping them in cool storage.

You in Texas may wish to leave them in the ground and trust you don't get a killing winter.

(Bubbling this thread back up.)

I too am new. I have one Dahlia from WalMart. And would like a beginners primer, a link would do, I can still read with the prescription eyewear. I am in the high deserts where zones don't mean much. Here in September we are occasionally seeing frost on cars but daytime temperatures may nudge 90°F. I am located on an ancient sand dune so I either plant in sand or buy a sack of something.

That's it, you found it Albert; a great comprehensive place to start. I wonder how long you will have just one dahlia.

My lone dahlia from WalMart got frost. Leaves turned and flowers turned dark and the leaves curled under so I clipped it to the ground and went looking for a digging tool but got distracted. It has been a week and now the thing is growing again. New leaves.

It will frost again. Do I wait or dig?

Perfect time to dig! Don't worry about the new shoots, but when you go to divide whatever bounty might lie underground in the form of tubers, use those shoots' locations as little green guides on where to cut at the stalk/tuber junction. You'll hopefully have a viable, strong-necked tuber next spring with nearly guaranteed growing potential.
Good luck!

finally i see a bud on my dahlia...will post a picture.
i cant believe its blooming so late.i still could not figure out tthe sun exposure for the plants though.
rema