These root vegetables take up to 4 months to mature, but because frost enhances their sweet, delicate flavor they're a favorite with gardeners in areas with short growing seasons. If soil is mulched so it doesn't freeze, parsnips can be left in the ground and harvested all winter. If the ground does freeze, they can be dug the following spring. In warm regions, parsnips can be planted in the fall for use as a winter crop. Approximately 500 seeds per packet, plants 25 to 30 feet of row. An ounce (average of 5000 seeds) plants 200 feet.