How to Divide Dahlia Tubers
I find it best to divide the dahlia tubers in the spring just before planting, at this time the eyes will be more visible than in the fall, making it much easier to divide, especially if you are a beginner.
Dividing the tubers is important, if you keep planting the tubers outside every year without dividing it will become a “root bound” mess. Just picture trying to grow a large plant in a little pot, when you remove it from the pot and look at the roots it becomes way to overcrowded and root bound. Dahlia tubers can do the same kind of thing. If you do not divide them the tubers can become very congested, and run out of room to grow.
When dividing the tubers you have to make sure that for every root you have an eye, if you just cut off the root it will not grow. For beginners it may be easier to just cut the clump in half or three pieces, until it becomes easier to tell where the eyes are and what they look like. Just be sure that every clump has at least one eye. This is what I did when I first started saving dahlia tubers, and slowly every year I was able to cut them up better and better, till finally I could divide the tubers up so almost every root has an eye.
Below: The first photo shows the some visible and still dormant eyes the second photo shows where you could cut in order to have an eye at least one eye for each tuber. The cuts from this photo would give you 4 separate tubers to plant.