These radishes can be sown anytime spring through mid summer however, radishes prefer cool weather, so they will be milder if planted in summer for fall harvest.
Direct sow seeds outdoors 4/1 – 8/1. Plant seeds ½” deep, 2" apart in rows spaced 18” apart. Thin plants to 4-6” apart. Days to germination: 3 - 6 (longer in cool soil). Keep seeds and plants consistently moist. Use crop rotation to avoid diseases (all brassicas). If necessary, cover with row cover fabric to protect against flea beetles and cabbage root maggots.
For large, straight roots plant in loose soil such as sandy loam or raised beds.
Harvest radishes when they reach full size. If weather is hot, do not leave roots in the ground too long or they will become pithy. If temperatures are cool, radishes can remain in the ground longer. Use a garden fork to loosen the soil before pulling up otherwise the roots will break. This type of radish stores well; it is milder if harvested during cool weather of fall.
Biennial radishes need exposure to cold temperatures in order to flower and produce seed so plan to grow them to be mature in the fall. Radishes are insect pollinated and are cross pollinated – they will cross with all other radishes that are blooming nearby. Isolation distance: ½ mile. Minimum population size: 10-50. Dig radishes and identify best roots for replanting for seed (clip off leaves before replanting). Space 2 - 3 feet apart. Stake plants. Clip seed pods when seeds are fully ripe. Lay out to dry.
