Sowing: 

Since mustard garden seeds thrive in cool weather, Florida Broadleaf mustard seeds taste best when grown as an early spring or fall crop. For a spring crop, direct sow the seed in full sun and rich soil about four weeks before the last expected spring frost, and lightly rake them into the soil. Keep the rows 10-12" apart. When the seedlings emerge, thin them to 5-6" apart. For a continual harvest, plant more mustard every 10-14 days. For fall planting, plant the seeds in late summer or early fall about 10 weeks before the first hard frost. Climates with warmer winters may be able to grow Florida Broadleaf mustard seeds from fall to spring.