The Nutrients That Radish Seeds Need to Grow

Nutrients

• Radish seeds need phosphorus, nitrogen and potassium in large amounts. Phosphorus is responsible for strong root formation in radishes. This nutrient can't move through the soil, so it must be present near the radish seeds. Nitrogen is responsible for healthy leafy growth, while potassium aids in photosynthesis. Radish seeds use small amounts of iron and magnesium, which aid in the development of chlorophyll.

Before Planting

• Prepare the soil before planting radishes by spreading 2 to 4 cups of balanced 10-10-10 fertilizer over the soil and digging it to a depth of 6 inches. Apply the smaller amount if you have rich soil to begin with. Apply the larger amount if the radishes are following a heavy feeding crop, such as squash or tomatoes, or if your soil is poor.

Growing Season

• Once radish plants appear, side-dress them with 1/4 cup of nitrogen per 10 feet of row. This extra helping of nitrogen encourages fast growth. A few shovelfuls of manure makes a good organic substitute. Use well-aged, composted manure only to avoid introducing pathogens into the garden.

Considerations

• In addition to fertile soil, radish seeds need evenly moist soil to germinate and grow. Plant them in full sun and thin the plants to three to six inches apart when they stand 1 inch high. Most gardeners grow radishes in the spring, but winter radish varieties are suitable for the fall garden. These radishes take longer to mature and may be red, black, white or pink. Try White Chinese, China Rose or Round Black Spanish fall radish varieties.

General Soil Preparation

• If you've never planted a vegetable garden before, take a soil sample to a university extension or commercial lab for a soil test. A soil test not only tells you what nutrients are deficient in your soil, but also the pH level of the soil and the amount of organic matter in the soil. The soil test analysis will offer recommendations on fertilizers and other amendments to improve the soil. Add lime, if necessary, to raise the soil pH, and compost or manure to improve texture and drainage. Radish seeds are very small and germinate best in fine, slightly sandy soil. Till the soil and rake it to create a fine seed bed for them.