These root vegetables take up to four 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 will plant a 15 foot row. An ounce contains 5000 seeds and will plant a 150 ft. row.