Answer: Dahlias grow from tubers and once you plant a single tuber the plant will develop and whole set of tubers, all around the original one, like spokes on a wagon wheel. Each of these attached tubers can grow into a new plant so carefully separate the tubers by cutting them off where they are attached to the main stem. Each tuber will have buds or eyes at the top so look carefully for them. Plant the individual tubers with the eyes facing upward - that's where new stems will develop.
If you plant the entire clump instead of separating them, you will get lots of new stems. In this case, the tubers can be planted down with the stem they are attached to facing up towards the sky.
Hope this clarifies things for you.
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