Growing rutabagas involves planting in time for a cool-weather harvest, watering consistently and enriching the soil with compost. Rutabagas need about 90 days to mature, and gardeners in cold climates should plan to harvest the roots just before the first frost.
Warm weather hinders root development, so gardeners who live in warmer areas must plant in the fall once nighttime temperatures are below 60 degrees Fahrenheit. Rutabagas grow best with consistent watering, as occasional soakings can cause the roots to split. Rutabagas need plenty of room to grow, and gardeners should place plants 12 to 18 inches apart. The roots are ready for harvest when they measure 3 to 5 inches in diameter.