Parsnips need loose, fertile soil, and are cultivated similar to carrots. They prefer to be planted in a cool spring soil, and can take up to 3 weeks to germinate. Plant no more than 1/2 in deep in rows approx 18-24 in apart, thin to 3-4 in apart. Parsnips are best grown over an entire season and harvested only after hard frost for the best flavor. They will keep in the ground over winter for a continuous harvest (assuming the soil isn't frozen solid) with the best of the crop harvested in spring before new growth begins.