Parsnips need sunny, well-drained soil that has been deeply worked. They do best in sandy loam or raised beds. To help aid germination, soak the seeds overnight in lukewarm water. Drain before planting. Plant two weeks before last frost so as to be mature by late fall.
To sow the parsnips, mark rows 18" apart using long wooden dowels or a broom handle. Plant two or three seeds 1/2" to 3/4" deep every two inches. Cover the seeds by pushing the soil back on top of them. Be sure to not compact the soil on top of the seeds as this can prevent them from germinating. Water seeds.
When parsnip seedlings emerge, thin to one plant every 4". It is important to thin the seedlings before crowding impairs their growth. Thin by cutting the tops off the young plants rather than by pulling them, which can disturb the remaining seedlings by damaging their roots.
Parsnips need a good supply of water and prefer very lightly damp soil. Make sure parsnips get 1" of water every week either from rain or by watering. Parsnips reach maturity in approximately 100 to 120 days. Harvest after the first frost or as the need arrives.