Digging, Dividing & Storing
When the growing season comes to a close it is time to decide if you are going to leave your tubers in the ground or dig them up and overwinter them indoors.
Leaving in Ground
In the PNW, if you have well draining soil, your tubers have a better chance of surviving over winter if you choose to leave them in the ground. If you have soil that gets very cold and/or floods I do not recommend leaving them in the ground, for risk that they will freeze or rot. Those who leave their dahlias in the ground suggest covering them with a heavy mulch or even tarp to help keep them warmer and dryer.
Digging
After at least 120 growing days or your zones first hard frost, you can begin digging up your tubers to store them inside for the winter.
Very carefully with a shovel or a pitch fork, gently work the soil about 18 inches away from the center stalk of dahlia. You planted one small tuber, but it will now be a large clump of dahlias. Carefully work your way around and under the clump and gently lift the clump out of the ground. I do not suggest holding the center stalk and pulling, you risk breaking the clump. Take caution not to slice your tuber clump.
You can either wash your tuber clump at this time or leave soil on before packing away for storage. Allow clumps to dry before storing.
Dividing
Before you begin dividing tubers, learn their basic anatomy. If tubers are divided incorretly, they will not grow into flowering plant. To be viable, a division needs an eye on the crown, a neck and a tuber.
Storing
There is no sure way to store dahlia tubers. Most importantly, you will need to control temperature and humidity throughout the winter to ensure your tubers safely store. Identify which storage medium you will use and keep tubers in a dark cool space all winter long.
Temperature: Dahlia tubers do not tolerate freezing temperatures. Ideally, keep dahlias between mid 30s to mid 40s. Too cold, your tubers may freeze. Too hot, your tubers might think it is the to wake up and will start growing.
Humidity: Your dahlias will appreciate a higher humid environment. This will help tubers retain their moisture. Humidity that is too high can end up creating an environment for mold and rot.
Storage Medium: There are several different options for storing tubers including (1) saran wrap, (2) vermiculite, (3) wood shavings and (4) peat moss.
It is best to experiment with different methods and find out which best works for you in your storage space.
At Kale Lane Dahlias we wash off the soil, divide clumps and store individual tubers right as the growing season ends. We cut, label and put tubers into labeled bins or bags full of vermiculite for the entire winter. Tubers are entirely covered in vermiculite to help reduce the risk of mold.
It is wise to check on your tubers periodically to check for signs of rot or mold. The sooner you can catch either of these the easier it is to take care of them without losing them.
