Prepare a 12-inch-diameter turnip container in early spring four to six weeks before the last expected spring frost. Combine 1 tbsp. of a balanced slow-release fertilizer with the moistened soil inside the pot.
Sow the turnip seeds a half-inch deep in the prepared soil. Space the seeds 2 inches apart in all directions inside the pot. Seeds typically germinate within seven days.
Place the pot in a sunny location. Water as often as necessary to keep the soil moist without making it soggy.
Begin harvesting the greens once the leaves are about 6 inches long. Cut off the entire green top of the plant with a sharp knife, leaving only a 2-inch stem attached to the root. The stem grows a fresh set of leaves for later harvesting.
Fertilize the turnips with a soluble fertilizer beginning after the first harvest. Apply a 10-15-10 fertilizer at half the label-recommended rate every two weeks through the remainder of the growing season.