Planting Dahlias Dahlias tubers should be planted in the spring after the risk of frost. Here in Endless mountains Pennsylvania, that is usually about a week after mother's Day.
Dahlias can take up to 8 weeks to emerge after planting. Dahlias also prefer to be grown in full sun, although you can successfully grow them in areas that receive sun 75% of the day. They can be grown in pots but make sure you are using a container large enough, most varieties should be grown in a 5 gallon pot. It is best if soil temperatures are above 55˚ F when planting. In addition, your soil should be moist, but not wet. Like storing dahlias, too much moisture around a dahlia can cause rot. You don’t need to worry about watering dahlias until they are at least 6” tall. Over watering at this stage can stunt strong root growth. Allow them enough space, some varieties can become quite large and planting too close can cause plants to not receive enough light or air flow which can lead to mildew. We plant our dahlias at a depth of 4-6" in the ground. Dahlias should be planted on their side with the eye facing up. If there is no eye visible at the time of planting, don't worry the eye will find its way to the surface. When planting in a single file row, you can plant as close 8”. When planting in a double row, it is best to stagger the planting.
When doing a triple row, stagger the planting and plant at 10” apart.
For walking paths between dahlias, leave a minimum of 45” between rows of plants. When the plants are mature, you will have a hard time walking down your paths if you don't leave enough room for you!