If planted among greens, such as turnips or mustards, radishes will serve to deter insects from invading the greens. The majority of radishes are grown in the cool spring and fall months, but there are some varieties which will tolerate the heat of summer. Allow enough space between plants to insure the roots have enough space to develop. Radishes planted too close together will produce all tops and very small roots. Cabbage loopers , Flea beetles , Harlequin bugs , Imported cabbage worms , and Onion maggots .
Spring planted radish takes about four weeks.
The summer and fall varieties take five and nine weeks respectively.