Though full sun is best, parsnips can handle some shade as they are a cool weather crop. The most important factor when it comes to growing parsnips is making sure that the soil is well-loosened. Use a shovel to loosen the soil in your planting area extremely thoroughly. Remove any rocks or hard, clumpy soil from the area. Use a rake to catch any small stones. You want the soil to be fluffy rather than hard and clay-like. If the soil is too clay-like, you can soften it by adding organic matter (such as yard trimmings or manure), sand, or compost to the soil. If you do not do this, the parsnips will not reach a good shape. Mix in about four inches of organic compost into your soil. This will help the seeds germinate in the soil and encourage a hardy production.
Begin to sow the parsnip seeds three weeks before the last spring frost.
Parsnips like a cool climate. If you are planting in USDA hardiness zone eight or warmer, you should sow your parsnip seeds in the fall or winter.
You can broadcast your seeds at random or plant in rows. If planting in rows, space the seeds about 1–2 inches apart in a shallow trench, no more than 1⁄2 inch deep. Space each row of parsnips 8–10 inches apart from each other.
The seeds will take about one to three weeks to sprout depending on the temperature of the soil. The colder the soil, the longer the seeds take to germinate.
Water the parsnips very carefully after planting.
Keep the soil moist at all times. If you are in a hot climate, this means watering your parsnip plants daily. Just be sure not to wash away the fragile seeds or harm the sprouting seedlings with too much water pressure.
Apply mulch to sprouting seedlings. Add a few inches of a leaf, bark, or hay mulch to the ground around the seedlings to seal in the moisture. Pull out any weeds that develop through the mulch by hand. Do so gently so as not to disturb the parsnip roots. Be sure to cover any part of the parsnip itself that begins to grow out of the ground with mulch. If the parsnip crown is exposed to the air, it will become bitter.
When the tops of the parsnips reach two inches high, thin the parsnips to one inch apart by pulling the small parsnip plants out of the ground. After another two weeks passes and the parsnip tops have grown several inches high, thin the plants again to three to four inches apart. Be sure not to skip this step, as crowded parsnips will not grow straight and may not develop fully.
The bigger and longer they grow, the sweeter and juicier they become. However, you can pluck and eat them as soon as they grow big enough to eat, which usually is about 4 months after planting.