The first thing I'd look at is moisture levels, especially down near the lower part of your cuttings (not surface level moisture). This is the most likely area for problems. After that, it could be a lot of things. It would help to know more about what exactly happened to your cuttings (did they just sit there never grow roots, did they rot, or what). Also, even greater specifics on what you did (type and method of rooting hormone, when you took the cuttings, etc) would likely be very helpful.

Henry, plants sense what time of year it is through light, heat, humidity and other factors. We can't root plants very well even here in Florida from November through February. Plants root best during the active growing season when all of the conditions are favorable. For us, that is March - September. You may think you have perfectly replicated those conditions artificially but ask anyone who has a salt-water aquarium how difficult that actually is. Bottom line is that your timing is all wrong. You are working against all of the forces. Plants want to remain dormant right now, not put down new roots or new growth. Try again with a vengeance - for you, probably in May, June and July - and let us know how it goes!

"Bottom line is that your timing is all wrong."

There is no basis, as of yet, to believe that is true. In fact, there's reason to doubt that propagation was tried anytime recently, since it's the middle of winter. Still we don't have any information on timing!
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Since this was a double post, I will provide a link to the other post below, for anyone interested.

Here is a link that might be useful: Duplicate Post in the Dahlia Forum

No, timing is a bit extreme - miles too early imo.

I'm not sure it's the timing. However, I do know that tubers in storage will start to push eyes in April even if the temperature and humidity are the same as they were in January. So, maybe they do "know".
I'm starting early in an attempt to increase some varieties. So, I may not necessarily keep anything that I root now.
Henry

"No, timing is a bit extreme - miles too early imo."

Campanula, can you tell us how (before Hvander's last post) you determined when the cuttings were taken or attempts were made to propagate? I'd sure love to know! If you have access to a crystal ball, I need some predictions from you!

Brandon, I can root almost anything in March and April. I can root almost nothing in November through February.

Exactly! That's why it's good to know "when".

edit:
...and why I asked in the very first response.

This post was edited by brandon7 on Fri, Jan 31, 14 at 21:56

cuttings taken any time around now are going to be waiting almost 5 months to go in the ground outside....why would you want to raise these plant with all the fuss it entails, keeping them warm and light.
This was the second dahlia post I replied to (and possibly conflated the two) so I generally assume that people are talking about doing it now rather than some unspecified time in the future (as, I believe other posters implied).

In this thread, the original poster clearly indicated the attempts were in the past. It does seem to have been a source of confusion that multiple posts had apparently been made by the same person about the same subject and even in this same forum. I was not aware of the previous post, and that is why I asked WHEN the work was done. I'm not sure how the future comes into play here, but the confusion, by people that had read the other post, about my timing question is understandable, I guess.