There's a lot of info on the Colorado Dahlia Society site. Look under Topping, Trimming & Disbudding.

Here is a link that might be useful: Colorado Dahlia Society

I just came in from pinching a fair number of mine tonight. What I do is look carefully at it, and when I see at least 2 sets of leaves, I use my fingers and pinch off the top just above the 2nd set of leaves. That forces the plant to send up new shoots from the leaf nodules, and hence we get the bushiness that you seek.

I was going to take pictures, but it got dark too fast and started to rain, so I had to bring them all in as we are expecting near 0*C tonight, again. Will warm weather ever come?

Jroot, I will not complain about our nonstop rain seeing your chilly expected temperature.

I top/pinch the top growth shoot only when the plants are about 15-18 inches tall. Don't worry about the side shoots or laterals, leave them be. They will deliver you flowers later.

I have a question: I always carefully fold back the little, tiny leaves on that top shoot and pinch out only the center growth, although from the photos at MidIsland Dahlia Society it seems I can just quit that nonosense and hack off the entire top shoot. Is that right?

I just pinch off the whole top. Seems to work.

I gave a friend a dahlia that was sprouting, and then she took off to England for 2 weeks or so. Her daughter watered it once in that time, and it was indoors. Today my friend told me that it was about a foot and a half tall, but really lanky. I suggested that she pinch it off fairly low ( above 2 leaf sets) and let it come back up, but she should be getting it outside when possible.

Do you agree?

Thanks for the tips, link, and reassurance. I am so excited about my dahlias! I saw some that were fully grown in a greenhouse last week, and blooming. WOW! such gorgeous bright flowers. I love the kinds that have three colours - the tips one colour (deep lilab), then another colour closer to the center (white), and then a core or heart of intense green or yellow. They are so beautiful. Altho I am a long way from having mine bloom (it is early in the season and cool here).

Some of the dahlias are about 9 - 12 inches tall and have 3 or 4 leaf pairs is that tall enough or to tall to pinch back....i'm so afraid i'm going to mess it up!

DapperDahlia,
I am assuming you are using your dahlias for cutflowers. There are only a couple of varieties that we pinch. Normally, we don't pinch any of the others. And, they're just fine. In other words, at 12" I wouldn't worry about it.

thank you flowerfarmer what i've been reading is that if i pinch them back it will bloom better...I hate to question you but will i still have flowers to sell?

From the Colorado Dahlia Society website:

"Disbudding is not essential to grow dahlias with fine blooms. In fact, if a dahlia plant is not disbudded it will produce many more blossoms than a plant that is disbudded. Disbudding, in addition to topping, is done in order to produce larger and fuller blossoms. Disbudding directs most of the energy saved, by removing some buds, to the remaining bud causing it to grow larger in diameter and in depth. Disbudding does not affect the form or color of the blooms.

thank you i'm sorry i questioned you....i appreciate your help

Flowerfarmer, why do you pinch only those certain varieties? Just out of curiosity.

I always disbud because the stem length on the main flower is so much better without the 'tagalong' side buds going on to develop. They seem to invariably break for me.

The tagalong side buds in a bouquet help sell the flowers at market. Customers love that. Is that what you were asking Pooch? We don't necessarily want huge blossoms that may be desirable in your garden. And, we get more blossoms per plant. One that comes to mind that we do pinch is Almand Joy. Otherwise, it will get a short but huge blossom right there down in the middle of the plant. Drives me crazy.

Yes, that is what I was asking. I find the tagalongs get in my way and invariably break- at least on the varieties I have allowed to proceed to that point. But if it works for you and your customers, great.