The radishes came up quick, filling the garden canopy completely that fall, and the following spring we found the plot was clean of weeds and rows of open holes were left where the radish roots had been growing. Well, we had a few extra onion plants that spring and decided to plant them in these holes, since we already had very clear lines laid out for us and a clean seedbed. What we got were the best looking onions that have ever come out of our gardens.