Daikon is a popular radish which is pickled and cooked in a variety of ways. Here in our garden, it has a small head relative to its root size. As all tubers which have been planted in our garden, the root seems to "send out" its initial tendril towards the cold pipe, and then it grows along the tendril. Our tubers are as long as the cold water pipe is deep. This explains the small head size; our root is thicker at the bottom where the pipe is located, and tends to taper off more slowly than other tubers. You can refer to the article on carrots, here in this garden book. Carrots are another incredible example of how the tendril seeks the pipe.