Dahlias Through the Seasons: Winter Tuber Dividing

One of the most daunting and tricky of tasks can be dividing your dahlia clumps. Out of the ground, they are an intimidating mass of tubers that benefit from division. Like perennials, dahlias benefit from division every year, or every few years, because they will begin to compete with each other for nutrients, leading to fewer flowers. Dividing your dahlia clumps is beneficial for the plants and a great way to multiply the number of plants you put in the ground next year. The other is taking cuttings which will be discussed in a separate Winter post.

You have dug your tubers out of the ground and you are ready to divide. This may happen days after you dig them or after several months in storage. The timing is up to you and what works with your storage method. Choose your storage method BEFORE deciding on when to divide!

Winter Divide:

I divide in late winter, usually February, when I am ready to start waking the tubers up and when I start taking cuttings of the dahlias I wish to have more of. The cons: tubers have toughened up so it is more difficult to divide the clumps, eyes are less visible than just after digging (but easier to see if they have begun to wake up), it is a messy process so use a drop cloth. The pros: tuber clumps overwinter better (for me!), I have limited time in the fall to divide, and it gives me a physical task to tackle in the dead of winter.

Fall Divide:

I recently dug and divided a clump for the purposes of this blog and I it is SO MUCH EASIER! The tubers are soft and have. not toughened up from months in storage, the eyes are a little easier to see (although still tricky), and all the washing can be done outside. However, storage becomes a bit more difficult unless you plan on the Saran Wrap method or bins with vermiculite. The conditions for storing single tubers needs to be a bit more precise than if storing as whole clumps protected by a layer of soil.

Let’s Divide!

Grab a pair of sharp, sanitized(very important to prevent the spread of disease, disinfect between every tuber clump) snips. Mine are straight blade and come to a fine point which makes it each to get into small spots in the tuber clump. Dig up and clean off a clump of tubers, using the high spray on the hose if just dug or, if coming out of storage, a paintbrush works well for dusting off excess soil.

Study your clump- identify where the stalks attach to the tubers (this is the crown portion), the necks (can be short or long), and the tuber (large storage body). Dividing just after digging also allows you to identify the mother tubers (the original tubers which look more wrinkled and dark).

You will also notice that each stalk has a group of tubers attached to it. These might be intertwined with each other but it is a good place to start when dividing. At this point, you can clean up the ends of the tubers by trimming off any roots or long tuber tails.

I have three methods of dividing: look for eyes and cut out those tubers, divide by stalk clumps, and when clumps are very large, divide into smaller more manageable pieces before seaching for eyes or natural divisions.

What is an eye?

The eye is where the tuber will begin to grow. A tuber will not grow without an eye. The tuber can look perfect in every way but without that eye, it will not grow. There will be tubers and casualties when dividing, not to worry, happens to me all the time! Check out some examples of eyes found on the crown. These eyes will also require an energy source so make sure to keep that tuber well attached.

Step by Step

When I am doing something unfamiliar, I want to see all the in-between steps and zoomed in pictures. I will do my best to break down this clump in a way that helps you to do the same to your own tubers. The first time I attempted this process, I was petrified! Now I know I will lose a few tubers, break a few necks, miss a few eyes (or make up a few), but, the end result is more viable tubers than I started with. The more you study the tubers and the more you divide, the more comfortable you will feel performing this not so delicate surgery.

Step 1- Study

Find the mother tubers- these can be cut away or saved depending on how they look. These were pretty rough so I decided to cut them off.

Trim the roots and long tails.

Identify the stalks and where they connect to the tubers.

Step 2- Start easy!

This stalk connects to a fresh set of tubers and stands out from the others. It makes for an easy first cut. It will also allow me to cut the mother tubers away since they are located just below this newly formed clump. An eye is visible above one of the tubers which makes it viable for next year.

Step 3 - Separate

Carefully untangle any tubers as you life away the piece you cut from the main clump. Set it aside for further dividing if necessary.

Step 4- Eliminate rot, mother tubers, tubers with broken necks, and any other standouts

Below, I removed two mother tubers that were a bit rough looking and a tuber that showed some rot/damage. Both could have caused trouble in storage so it’s best to remove. I also removed a tuber with a broken neck, it will not grow even if there is an eye.

Step 5- Make another cut!

Keep looking for natural divisions in the tuber clump. When you find one, insert your snips into the clump, starting shallow and going deeper if necessary. Check the bottom to avoid damaging tubers below when cutting. If you spot an eye with a tuber attached, cut it out of the clump. Make sure the eye is fully attached to it’s energy source or it will not grow. If it is in a tricky spot, continue dividing easier pieces until you come back around to it.

Step 6- Find the Eyes

After you divide the clump into smaller pieces, check for eyes. These may be obvious or they may be hard to find. I was able to find two single tubers with eyes that I cut from the main bunch. I also found eyes on three smaller clusters but I was not confident enough in dividing them further because I could not find more than one eye on each. At this point, I would rather have a few tubers together with an eye which can be divided further in the spring if another eye shows up. In the end, I have 5 new plants for the spring!

Step 7- Label!

Label your tubers with a sharpie or tag and return them to storage or begin the process of waking them up for spring planting or cuttings.

Troubleshooting: Disease and large clumps

Check your clumps over for signs of disease, mainly gall. Gall is a bacterial infection that can spread from plant to plant. There is leafy gall which is an unnatural number of shoots growing from the stalk or crown gall which are abnormal growths where the tubers meet the stalks. In both cases, dispose of the infected tubers in the trash and disinfect all tools used. Avoid planting in that area of soil for a few years.

I have stared at large clumps for a long time before attempting to make that first cut. Dividing the whole thing in half helps to make it more manageable. Clean up any broken necks or rotting pieces and it will start look a bit easier on the eyes. When in doubt, keep a few tubers together with the crown and odds are, an eye will appear and it will start growing come spring.

Good luck with your dividing!

If you have any questions, let me know!