Certified GKH Gardening Expert
Turnips need somewhat cooler temps and loose soil to properly form a bulb. If you are noticing more top growth and little to no bulb formation, it is likely due to a fertilizing/nutrient issue. While a soil test would allow you to know for certain, it may be that you have too much nitrogen and too little phosphorus. Lots of nitrogen will result in plenty of leafy growth but if your soil is lacking phosphorus, there will be poor root growth. I would add some more phosphorus, like bone meal, to the soil and give it some more time. Also, make sure the plants are adequately mulched to keep the soil cooler. Generally, it takes about 45 days from planting to see good-sized turnips for harvesting.