The second and third flush of blooms will have better stems. Good dahlia cutting varieties will always have nice stems. Some less useful varieties like Blackberry Ripple have nice stems only for the first and second flush and then are too floppy for bouquets, The pursuit of "early" blooming dahlias has some drawbacks like your problem.
Disbudding each flower stem so it has only one flower instead of the three that nature provides us is very useful also. Some varieties only have good flowers if you do this. Other, mostly smaller flowers do not need disbudding. Most cut flower operations do not disbud much. They pick the flowers with long stems(actually stalks as the stem is the part just above the first set of leaves). When you do this the plants sends up more laterals from below for more flowers.

Steve

I think your shade idea is a good one.

I have a 'dead' space behind a rose (pot) and dahlia (in a pot) in my 'purple' section and I planted a 'tall' Sean C tuber this year. Because it gets filtered light for many months (until it gets to 2 1/2 -3 feet tall when it can finally 'see' the sun) I noticed the main stalk was very spindly. I wondered if it was even going to last until it got to 3 feet but now it is and it looks like it will bloom.

However, the plant is very thin with sparse leaves which I attribute to lack of as much sun as my other dahlias get. So I suspect it is the shade that slowed it up.

Either that or Sean C is just spindly as a variety. It is supposed to get to 4 1/2 - 5' tall so maybe it is supposed to be that way but I think it was the lack of direct sun for it's first 2 months that causes it to look less healthy than the other near it.

Here's a simple shading system that sure beats using umbrellas for each plant!

Here is a link that might be useful: 60% shade cloth on cables with grommets

>> Here's a simple shading system

Yes, that's exactly what I need. I've got flowers coming out misshapen (open in the middle) already due to high heat and it would be great if the shade cloth would help stretch the stems too.