Growing dahlias indoors does not have to be difficult. I use this process every year!
What you will be doing is replicating the environment they come from in the higher altitudes of Mexico in order to wake them up. This will allow you to get a head start if Spring is coming a little later in your zone.
1. Select a storage container that is clear and place it where it will get indirect light. Do not use any dark containers because they will not allow light to filtrate. I have mine in front of my sliding doors.
2. Add 2″ or 3″ of soil. Make sure the soil has a little moisture but it is not wet.
3. Add Osmocote to the soil and mix well. The dahlias are not hungry until they begin to grow, so just sprinkle some on the soil to begin with and it will last the entire growth period, until you take them outside.
4. Place dahlia tubers next to each other laying flat on the soil (no need to bury them). If you have an eye, place the tuber with the eye on the top.
5. Create labels for each tubers, depending on how you lay them out. You can do a row of the same with one label.
6. Spray your tuber in the morning and late afternoon. It is good to keep the moisture level going but don’t over water. You do not need to water with a water dispenser until the growth is at least 2 in.
7. Optional step for cold climates: I add a small heater that I keep at 70 degrees Fahrenheit to wake up the tubers.
8. You now will have amazing growth on the tubers and healthy roots that will be ready to plant outside!