Parsnips grow best in full sun but tolerate some shade. The best soil type is loam but parsnips tolerate most soils. Prepare deeply and remove any stones or debris that may deform the roots. Plant seed 1/2 inch deep, in early April, in rows 18 to 24 inches apart. When plants are 4 inches tall thin to 5 inch spacings. The seed germinates slowly, taking as long as 2 to 3 weeks. Keep the soil moist to prevent crusts, or cover the seed with a sand and soil, or peat and soil mix. The row may be marked by mixing in a few radish seeds. Do not use seed more than 1 year old. If the garden was not fertilized use 3 cups of 5-10-10 per 50 feet of row. Rapid growth is needed for good quality roots. After thinning, apply a 2 inch mulch. Parsnips form seedheads prematurely if poorly grown.
Harvest parsnips any time they are of sufficient size. The flavor is improved by exposure to cold temperatures. The roots become woody when spring growth starts but they are not poisonous.