Requirements to Grow Radish Seeds

Planting Time

• Radishes germinate readily in cool spring soils, but they can also grow as a fall crop once summer heat is past. Plant radish seeds only after the soil reaches a temperature above 40 degrees Fahrenheit. This usually occurs two to three weeks before the last expected spring frost date in your area. The seeds germinate poorly at temperatures above 75 degrees Fahrenheit, so wait to plant fall radishes until after the soil temperature begins to drop. Soil temperatures between 55 and 75 degrees result in the best, most even germination.

Soil Preparation

• Provide a moist, well-drained garden bed in a location that receives all-day sunlight. Avoid areas that collect standing water after rain, snow melt or irrigation. Organic matter adds loose but absorbent materials to the soil bed. These materials allow excess moisture to drain away from the developing radish roots without drying out completely. Till a 2 inch layer of compost into the bed prior to planting to add the necessary organic matter. Radishes also benefit from a light fertilizer application prior to planting. Work 1 cup of 10-10-10 fertilizer into every 50 square feet of radish bed before sowing the seeds.

Sowing Method

• Sow radish seeds after the soil warms and after preparing the bed. Raking the soil surface provides a level, fine-textured sprouting bed that radish roots can penetrate more easily than in compacted soil. Sprinkle the seeds thinly along each planting row, sowing approximately eight to 10 seeds per foot of row. Space rows 12 inches apart. Cover the seeds with moistened soil – ½ inch of soil for regular radishes and up to 1 inch of soil for the larger winter radish varieties.

Germination Care

• The seeds sprout within one to two weeks if the soil temperature remains in the correct range and if the soil remains moist. Mist the soil surface with a light spray of water if it begins to dry. Avoid sharp sprays of water, as this can wash away the small radish seeds. Laying moist burlap over the bed retains moisture in the soil during germination and eliminates the need for watering. Check under the burlap daily and remove it immediately once the radish sprouts begin emerging. Thin the young plants so there is a 2- to 3 inch space between each radish once the seeds have all sprouted.