Plant the turnips in the outdoor garden only in early spring or fall. These plants thrive in cool, moist weather and may not survive hot midsummer plantings. If you're planting in midsummer or winter, use deep 5-gallon pots with drainage holes. If you're planting outside in spring or fall, choose a site that gets four to six hours of sun every day and quick drainage.
Mix or amend the soil for planting. Turn 4 inches of rich organic compost into the top 8 inches of soil through the bed to give the soil better nutrition and drainage. Mix 1 part organic compost to 1 part potting soil or bagged garden loam for pots, and fill the containers three quarters full.
Plant the turnips with their pointed ends down, at every 2 to 4 inches in the row. Leave any sprouting leaves exposed, or plant the rounded end of the turnip just below the soil surface.
Water the turnips with 2 inches of water every week and lay 2 inches of organic mulch over the soil around outdoor plantings to maintain soil moisture.