Growing Round Black Spanish Radishes

Plant Black Spanish radishes in late summer, 40 to 50 days before the first estimated frost. These radishes thrive with warm starts and cool growing seasons, but should harvest before the ground freezes.

Prepare a partially shady, quick-draining plot in the garden. Radishes don't need full sun, and some shade protects these moisture-loving plants during the heat of late summer. Don't plant the radishes in a site that puddles, though, as standing water leads to rot. Turn 3 to 4 inches of garden loam or organic compost into the top 6 inches of soil to loosen it and retain moisture for healthy radish growth. Throw out any rocks, which can stunt radish growth.

Plant Black Spanish radish seeds 1/4 to 1/2 inch deep at every 1 to 2 inches in the row. Leave 12 to 24 inches between the rows, and spread 2 inches of organic mulch over the soil between plantings. The mulch helps maintain soil moisture during the heat of the season.

Water the radishes with 1 to 2 inches of water every 4 days to keep them moist. Dry soil or heat keeps the radishes from growing. Check the soil moisture regularly and increase the frequency of your waterings as necessary.

Thin Black Spanish radish seedlings to very 2 to 4 inches in the row when they sprout to give them room for growth. Fall and winter radishes achieve larger size than spring radishes and need more room than their earlier cousins.

Harvest Black Spanish radishes after 50 to 55 days, when they reach mature size. Pull all radishes before the ground freezes.