When should I divide dahlia tubers?

Home gardeners usually divide dahlia clumps into individually viable tubers for replanting either in the fall, immediately after digging (also called lifting), or in the spring, after storing the clumps whole.

Why choose one or the other?

Dividing dahlia tubers in the fall

• Dividing in the fall drastically reduces the amount of space your dahlias take up. 

• You can count the tubers you have, which helps you plan your garden over the winter

• It spares you from having to do the task in the spring, when most gardeners usually have a lot going on.

Dividing dahlia tubers in the spring

• The eyes can be much easier to see in the spring as the plant starts to send out shoots in response to warmer temperatures, which makes dividing less challenging.
  

• It’s one less thing to worry about around the holidays (in the US, anyway).
  

• When you divide in the spring, you know exactly how many good tubers you’ve got. It’s normal for quite a few tubers divided, counted, and stored in the fall to fail over the winter, or to never develop a swollen eye or sprouts. 

Remember, if you choose to divide in the fall, you don’t have to divide right after harvest. Lots of more experienced gardeners who are comfortable spotting even dormant eyes will store their dahlias as clumps immediately after harvest, then divide them at their leisure over the winter.