Radishes can become lumpy if the growth cycle is uninterrupted. Radishes mature quickly–in 20 to 30 days. They need consistent moisture during this quick growth period. If the soil went dry, then the roots will react. Plant radishes in loose, humus-rich soil and keep the soil evenly moist. Mark on the calendar the day you planted then count ahead the days to maturity for the variety you are growing and mark the date for harvest. Don’t wait past the mature date, radishes will become “woody”, dry, and lumpy.