My radishes produce lush foliage, but don't develop good-sized roots. Why?
Excessive nitrogen, the rapid onset of hot weather, or overcrowding may produce plants that are all tops (lush foliage, little or no root development).
Misshapen roots and hot, pithy radishes are other problems that may be encountered when growing radishes. Overcrowding produces small, misshapen roots. Hot, pithy radishes may be result of hot weather or harvesting too late.