One experiment that turned out very well was another dahlia propagation. This one was to see if dahlias could be propagated without rooting powder as well as the ones I tried with rooting powder. The result? It's just as effective either way. Dahlias just seem to propagate easily.
I noticed that the propagation with rooting powder seemed to grow more roots from all over the dipped stem, but the important part is that roots grow so that the cutting gets water from the soil by itself.
I'd say, if you have a dahlia, just snip off a stem and try it.
The recent dahlia propagation experiment was on an orange dahlia that my mother brought home. It's just as lovely as the pink one I have, so I was waiting eagerly for some side stems to grow out so that I'd have a good-sized one to work with. Make sure you snip it off under a leaf node since the roots will grow out from the leaf node.
See the nice roots? Success! The best condition for propagating these cuttings is to place them into a shady spot out of direct sunlight. The sunlight dries out the cuttings too fast. Make sure you plant the cuttings into a sterile soil free of bugs that might attack the cutting. The container should have good drainage so that you can water the cuttings daily to keep the soil moist without drowning the plant.
You can see clearly where the roots grew out from in this picture. Notice that it comes from the leaf node instead of the base of the cutting. For the cuttings that were coated with rooting powder, the roots also grew from the stem area above the leaf node. It was kind of an explosion of roots. I'm not actually sure if that's a good thing. I read something about fibrous roots being a bad thing, but I wasn't sure what that meant.