Too much water leads to root rot, while not enough causes splitting and hotness. If you get the seeds in the ground two to three weeks before the last winter frost, they'll be ready for eating radishes in 25 to 45 days. Radish seeds must remain moist for proper germination and sprouting to occur. This process takes five to 10 days. Implement a dedicated watering routine once the radish leaves appear. Proper watering practices ensure an ample amount of flavor and crunch.
Pull out all weeds and keep them out during radish germination. If the seeds have to compete with nutrient-depleting weed roots, growth and yield will be stifled. Place a surveyor's stake at each end of the row where you'll be planting the seeds and then tie a string between the two. If any plant grows that isn't beneath this string, rip them out. Early and daily weeding practices will keep both you and the radishes from getting overwhelmed.
Preparing the Soil
Wait for the soil temperature to remain above 40 degrees. Rough up the soil with a garden fork and mix in 2 to 4 inches of organic compost. Apply 2 to 4 cups of all-purpose fertilizer over every 100 square feet of soil. Work the compost and fertilizer into the first 6 inches of the seedbed. Radishes do best when grown in sandy, well-draining soils. If you have clay-type soil, amend it with 3 inches of peat moss. Mix the peat moss in with the soil.
Plant the seeds 1/2 to 1 inch deep in a row beneath the string. Spacing doesn't matter at this point, but try to plant a seed every ½ inch. If you want more than one crop, plant new seeds every 10 days while temperatures remain below 80 degrees. Hotter temperatures make radishes bitter and hollow. Spring and fall are the best times to plant radishes.
Radishes need water, but not too much. Radishes will thrive in a seedbed with proper drainage. Keep the soil evenly moist, but not soaked. Don't allow the soil to completely dry out before watering. This causes the roots to crack. The soil should always feel wet to the touch. If you live in an arid climate where evaporation is a problem, mulch around the plants with a 2-inch layer of lawn clippings. The mulch keeps the weeds down.
Pull up ripe radishes after 25 to 45 days. Shake off the soil and wash them clean. Cut the leaves and root tip from the bulb with a sharp knife. Store uneaten radishes in the refrigerator inside a water-filled dish. The water keeps them from drying out and cracking.