Splitting Dahlia Bulbs

Once a dahlia has grown from a seed, it produces roots that appear to look like a bulb. Actually multiple dahlia bulbs are clumped together to look like a bulb but they are more like a sweet potato or yam. These roots are called tubers which are harvested and can be split off to create multiple plants just like the parent plant.

Step 1 – Collect the tubers

For next season, dig up, clean and store the clump of dahlia root (bulb or tubers) after the first frost when the plant starts to die. If you don't you risk losing the tubers once they succumb to freezing temperatures.

Step 2 - Separate the tubers

Splitting the bulb encourages growth for next season. Individual tubers can be discarded if they deteriorate during winter storage. The clump can be stored over the winter in one piece, and split in the spring before planting.

  • Use a sharp knife to divide the dried stem from the tubers. Usually three or four tubers will be tied to the stem and as long as one piece of stem is left on top of the tuber, it can be planted.
  • Remove the excess rootlets and material from the tuber.
  • Discard any damaged or rotten tubers which will not survive storage. Any cut surfaces should be cleaned and allowed to dry before storing. Lay them out for 3-5 days in a cool dry place.

Step 3 – Select tubers

Those tubers directly from the stem will have "eyes" and will produce the best plant for the season. Tubers which do not have eyes can be kept until the following season. A firm, strong tuber will produce the best results. Weak and soft tubers that show signs of shriveling rot or decay will not sprout and produce a plant. Reject tubers if the necks are thin and easily broken, these may rot in storage.

Step 4 – Trim and store

Clean and trim the tubers of extraneous rootlets and other extra growths. The tubers can be washed and treated with a fungicide to inhibit fungus growth. After washing, leave them to dry for a period of time depending on the humidity-low humidity will dry them out much faster. The tubers can be bagged to keep the same plant together.  A small amount of vermiculite will maintain the right moisture and temperature of the tubers. Store them in a light proof tub or dark place in the house.