How to Divide Dahlia Tubers

Are you new to dividing dahlia tubers? Or do you need a refresher since it’s been a year since the last time you divided a tuber clump? We can help! This is a tutorial all about dividing tubers. If you need help with digging, you can find that tutorial here. 

You can divide tubers in the fall or the spring. If you wait until the spring, the eyes on the tuber clump will often be more pronounced and easier to find. Some people don’t have space to store the clumps or just prefer to divide in the fall. Either time is fine.

After digging up your tubers, wash them off with water with your garden hose, or carefully brush away the soil if you prefer.  When all the dirt is removed, examine the tuber clump. 

• Look for the mother tuber. To identify the mother tuber, look for a tuber that is a little woodier and older. The texture is often a little different than the rest of the tubers in the clump. Sometimes we can even still find the variety name on the mother tuber!
• Check for any rot or squishiness in each of the tubers. If you find any, you’ll want to cut those tubers off and discard them.
• You’ll also want to look for signs of any potential bacterial infections like leafy gall or crown gall. If you find any evidence of disease, we recommend throwing those tubers out and then making sure to wash your hands and sterilize the tools you were working with.

Before going any further in the process, take a moment to make sure you’re working with clean cutting tools. We sanitize our pruning shears (aka flower snips), and our loppers and our bypass pruners frequently during the dividing process, even if the tubers we are dividing look healthy and clean. You can sanitize metal tools with heat, as we do (a propane torch with a trigger attachment works very well!), or with a part-bleach solution, or even with antibacterial/antiviral Clorox or Lysol wipes, depending on your preference.

We like to trim off all of the little feeder roots at the bottom of the tubers. This isn’t essential because those little roots will just dry up in storage, but it is tidier and sometimes makes the tuber clump easier to work with.

Now, identify eyes on the tuber clump. These will be toward the top of the tuber. They look like a little rough protrusion and they’ll be located around where the tuber attaches to the clump. (If you have rough protrusions on the tuber itself, those are most likely swollen lenticels. The eyes are different and will be on the crown of the tuber.)

The next step is to cut apart the tuber clump in such a way that you have as many tubers as possible with good eyes. If you have a particularly tidy tuber clump with the tubers all spread around the center evenly, it’ll be easier to divide than if you have a clump that is more closely clumped together. All of this is dependent on the variety of dahlia and even your soil conditions how your tuber clumps will turn out. 

• For a “spread out” tuber clump, go ahead and remove the mother tuber. If you can remove her and still have a good eye on there, that is great! Save her for next year. If you need to sacrifice a tuber in order to get into the clump with your snippers, the mother tuber is the one that should be sacrificed first.
• If you have more tightly clumped tubers, you may need to take a pair of loppers and chop the clump in half first before you start dividing so you can get to all of the tubers. 

With your snippers, start cutting into the stem/crown of the tuber clump , removing one “finger” at a time. Go slowly if this is your first time! Figure out which eyed tuber you can easily remove, go ahead and remove it, then stop and reassess and do this again until you have cut up the whole clump. There will usually be some “blind” tubers in the clump and you can just throw those out. Without an eye, it will never sprout, and you should discard it. We also throw away tubers with completely broken necks. As you divide more and more tuber clumps, you’ll get better at locating the eyes and figuring out how to get the highest number of tubers with eyes from each clump. There is definitely a learning curve, so don’t get discouraged if you make a mistake. 

If you’d like even more support, check out our online community, The Garden. The Garden is a rich resource for learning about growing dahlias and other flowers in your home cut flower garden, including lots of helpful videos, Live trainings, and first access to all of our sales. You can find more information here.