Why Radishes Grow Only Tops, No Bulbs

Radishes that produce lush greens but no swollen roots usually suffer from two causes: too much nitrogen fertilizer or too much shade. Nitrogen (the first number on fertilizer bags) fuels leaf growth at the expense of roots. My money's on over-fertilizing. Advise your friend to replant in March with zero fertilizer at planting. Full sun and lean soil grow the best radishes.