Turnips have two palatability windows: greens through fall (deer browse the leafy tops as soon as they're up) and bulbs after frost. The post-frost bulb pull is what makes turnips a late-season hunting tool — deer will dig through 6 inches of snow to get them.
Plant Purple Top, Appin, or Barkant turnip varieties 60-90 days before first frost. Pair with rape and kale for a complete brassica blend. Crop calendar pages have state-specific timing.