I tried last year for the first time and read up on it before.
I had a very/ too basic setup, just a windowsill, no aditional heat or light and 100% failure.

It seems to me that proper potting medium ( soilless mixture), good light and temperature are the key.

Aditional chemicals like rooting hormones or fungizide are not neccessaire according to really professional growers.

About the actual cuttings: I think you get more if you cut just under a node but perhaps someone else chimes in

There are some really good threads here in the Dahlia forum

Good luck, have fun, bye Lin

Here is a link that might be useful: Cuttings

invest in a heating mat, high humidity but good ventilation, no direct sun until they root. you need to catch the sprouts at that perfect moment when they are big enough but not at all hollow. that said, as with all cuttings, i find that paying attention is the most important thing.

linaria: Yes, like yourself, I only have a 'basic' setup. But did your cuttings consist of green growth only, or did you include a small portion of the tuber in addition?

I had tubers potted uop to give them a head start, and I just cut young shoots, leaving a rest on the tuber.

There were some debates about different ways of cutting or including a bit of the tuber.

As far as I remember that is not really neccessairy, it does not get you better results.

But no heating mat or additional lighting won't work.

It's like defying gravity, you can try but it won't work. There are some growing or botany rules, and if you get the conditions right, it just works, for all sorts of plants.

Go ahead if you just want to try, otherwise you can splitt your tubers to get more plants

Good luck, bye, Lin

When you remove a cutting from the tuber, you can cut off too much of the tuber material and destroy the eye that would have sent up many more sprouts. The standard and correct advice is to use a small scalpel(available at a feed store) or a very sharp knife and cut off the 2 inch sprout just above the tuber. The distance is about 1/16th of an inch or as the they say the depth of a coin such as a nickel. The eye will send up more sprouts and instead of cutting them off, you can rock them off and the eye will not be damaged(or continue using scalpel).
The correct temperature has been shown to be about 72 degrees(as proved by an experiment). They do not root well at warmer temps or cooler temps. Heat mats can be used but if you are doing them under florescent lights in your home, they are not needed or recommended. The use of florescent lights is important as they use the light energy to to grow the roots. They take about 12 days to root and that can vary by several days on either side. When the roots are about an inch or so long, the plant can be moved to a greenhouse if the temps there are not extreme. Most failures are caused by not using sterile pots and rooting medium. Pots should be soaked in a bleach solution. Rooting medium called germination mix can be bought and other mediums such as Oasis or rock wool work well too. Any potting soil with fertilizer in it will cause failure and no fertilizer can be applied to the cuttings until they have rooted and then only in very small doses.

teddahlia: Hi,
My aim is not to get as many shoots (offspring) as possible, but to see if sprouts attached to a variable amount of tuber are more successful than on their own. I have a few pot-grown tubers that are quite congested, making division difficult, and I'm interested to see if I can cut off the tops of the sprouted tubers and root them. I've read that some folk will cut off the bottom of a tuber so that it will fit into a pot for growing on. So it's a case of how much part-tuber (or how little) a sprout needs to carry on growing with a minimum of failures.

What is "on their own" ? Crowded, contorted, tuber clumps can easily be divided and as long as there is an eye, will grow. Tubers can be cut in half or even more and will grow just fine. When I divide tuber clumps that have small tubers, I leave lots of the stalk with the tubers so that they will have more tuber mass to draw from. I have trimmed many tubers and tuber clumps to fit into pots and it is my belief that as long as you have about as much material as a small chicken egg, they do fine. Rooting cuttings makes more sense to me as you are multiplying the number of plants from the tuber material. It is easy to get over 10 cuttings from a small tuber clump. You apparently are just ripping off some of the sprouts with a small amount of tuber material. That is really no different than rooting a cutting and I have done that accidentally many times and the plant material takes the same amount of time to root as the other cuttings I take. But there is no more eye to send up more cuttings.