When you receive your tubers, we recommend you check them and plant them as soon as possible. I like planting my tubers in small pots inside to start them out while they begin to sprout. I recommend using a porous potting soil mixed with compost (I like “Sea Soil” brand). Make sure to cover your tuber so the "eyes" don't stick out, which can lead to them drying out. Be careful when planting your tubers. The “eyes”(growth tips) are fragile and they may not grow if damaged.
Make sure they get good light and some moisture. However, be careful that you don’t over water the tubers before the plant develops as they can rot before growing. I water when I plant it, then once a week usually, or if it looks really dry. Sometimes I just mist the top of the soil every second day until sprouting so the soil doesn't dry out too much, but the tuber doesn't get too wet and rot.
Some people plant tubers (no sprout) directly outside, weather permitting, lying the tuber on its side in a hole already amended with compost or bone meal. If you are planting a dormant tuber (no sprout), they can be planted a little earlier as they are protected from light frosts in the soil. Personally, I prefer to grow a plant first indoors and then transfer the growing plant outside.
If you are planting a number of dahlias, it is recommended to space them around 2’ apart..
Do not over water young dahlia plants in order to avoid rot. As the plants get larger, a good rule of thumb is to water them if the rainfall is less then one inch a week. In the heat of the summer, or during dry spells I water large plants every two days if possible.