Multiply your dahlia collection by dividing tubers

Dividing dahlia tubers is a reliable method for gardeners to increase their flower stock for free, ensuring more vibrant blooms in the summer. The process, while intimidating at first, can be done in either the fall or spring with a few key steps. By splitting the large tuber clump that develops over the growing season, you can turn one plant into several new ones

When to divide your tubers?

You have two main options for dividing your dahlia tubers, and the best time depends on your climate and storage space.

Fall (After digging): Some gardeners divide immediately after digging up their tubers in the fall. The clumps are softer at this time and easier to cut through, which is especially helpful for dense varieties. This method also saves on storage space since the smaller, divided tubers take up less room.

Spring (Before planting): Many gardeners prefer to divide their stored clumps in the spring as the new growth "eyes" become more visible. This makes it easier to ensure that each divided tuber has a viable eye, which is essential for a new plant to grow.

Step-by-step guide to dividing tubers:

Whether you are dividing in the fall or spring, start by digging up your dahlia clump after the first killing frost has turned the foliage brown. Cut the stalk back to about 6 inches and gently lift the clump from the soil with a garden fork, taking care not to break the tubers.

Wash and inspect: Gently wash the soil off the entire clump using a hose or tub of water. As you do, inspect for signs of disease, such as rot or mold, and discard any unhealthy tubers.

Gather your tools: You will need sharp, sterilized cutting tools such as a knife, pruners, or floral snips. Use a solution of 1 part bleach to 10 parts water or rubbing alcohol to disinfect your tools between each clump to prevent spreading disease.

Find the crown and eyes: The crown is the dense area where the stem meets the tubers. The eyes, or growth buds, are the small bumps on the crown or top of the tubers. A new plant can only grow from a tuber with a viable eye attached.

Make the first cut: For large clumps, make an initial cut through the center of the crown to break the clump into more manageable sections.

Divide the tubers: Working one section at a time, use your sterilized tool to cut away individual tubers. Ensure each one has an intact neck connecting it to a portion of the crown with at least one visible eye. Discard any broken or shriveled tubers, as well as the old "mother" tuber, which is often darker and woody.

Label and dry: Label each divided tuber with its variety using a permanent marker. Allow the cut surfaces to dry and "cure" for 12 to 24 hours in a cool, dry, and protected location to help prevent rot.

Storing your divided tubers for winter:

Once your tubers are divided and cured, they need to be stored properly to survive the winter.

Select a container and medium: Place your tubers in a breathable container, such as a plastic tote with lid, cardboard box, paper bag, or bulb crate. Surround them with a storage medium like cedar shavings, peat moss, or vermiculite, which helps regulate moisture.

Find the right location: Store the containers in a cool, dark, and dry place where the temperature stays between 40–50°F. A cool basement, closet, or unheated garage often works well.

Monitor regularly: Check on your tubers monthly during the winter. If they appear shriveled, lightly mist the packing material. Cut away any signs of rot you find immediately.
With these steps, you can confidently divide your dahlia tubers and look forward to a garden filled with twice the blooms next season.