Radishes (Raphanus sativus)
Related vegetables: arugula, broccoli, Brussels sprouts, cabbage (all types), cauliflower, kale, kohlrabi, mustard, rutabaga, turnip, horseradish, collards, watercress
- Cool-season annual harvested for its swollen root before the plant flowers. Some winter varieties are considered biennials.
- There are many varieties. Spring radishes reach harvesting size 3-4 weeks after seed is planted, though some cultivars (sometimes called summer radishes) take a bit longer. Winter radishes, planted in late summer, take about 8 weeks to mature. They are often larger and more pungent than spring radishes. Oriental radishes (daikon and others) are discussed in a separate listing
- Small plant, ranging from 6-16” high.
- Plant spring and summer radish seeds directly into the garden starting 6 weeks before the average last frost date. Seeds germinate in less than a week if soil is at least 50 °F. Replant every 2 or 3 weeks continuing on until about 4 weeks after average last frost date or until temperatures average in the mid-60s. These varieties can also be planted in early fall as the weather cools. Time last planting so crop matures on average first frost date. Radishes are somewhat shade tolerant.
- Plant winter radish varieties starting in July in northern IN, in August in southern IN. Several plantings can be made. Time the last planting so crop matures on average first frost date. Remember these varieties take 2 months or so to mature.
- The first harvest of spring radishes can be made 3 weeks after planting. Small roots are sweet and mild. In general, harvest when roots reach 1-1.5” in diameter. The harvest window is short – radishes left too long become spongy (pithy) and hot. Many winter radish varieties are hot. Harvest when they reach the size for your variety. Winter radishes remain edible much longer than spring radishes. Estimated yield per 10 ft row is 10 bunches.
Plant radish seeds 1/4-1/2” deep. Thin to 1-3” for spring radishes, to about 6” for winter radishes (seedlings can be eaten). Make sure to thin. Crowded radishes do not produce good roots. If planting in rows, minimum row spacing is 12”, perhaps a bit wider for winter radishes. Spacing within a wide row is about 3”x3” for spring radishes. Because they mature so quickly, spring radishes are often planted with carrots and parsnips, between slowly growing cole crops, or between small tomato and pepper plants.