How to Grow Parsnips From Seed

Parsnips are a long-season root, so plant them in spring and harvest them in fall and winter. Direct-sow the seeds from a few weeks before your last frost through late spring, once the soil is workable and has warmed to about 45F. They need 100 to 120 days to mature, so an early start gives the roots time to size up before the cold. Always use fresh seed from the current year, because parsnip seed loses its viability faster than almost any other vegetable.

Parsnips send down a long taproot, so they need a deep, loose, stone-free bed. Dig the soil over well and remove stones and clods first, and skip fresh manure, which makes roots fork. Sow the flat seeds about half an inch deep and keep the seedbed constantly moist, because germination is slow and can take 2 to 3 weeks, and a single dry spell will kill the sprouting seeds. Sow a few radish seeds in the same row to mark it and stop the surface from crusting, then thin the parsnip seedlings to stand 3 to 4 inches apart. Do not transplant parsnips, as disturbing the taproot makes it split.

Once parsnips are up and thinned, they are easy and slow. Give them a steady inch of water a week to keep the roots growing smoothly, since uneven watering causes splitting, and mulch to hold moisture and keep down weeds. They need little feeding; too much nitrogen makes leafy tops and forked roots. Watch for carrot rust fly, whose larvae tunnel into the roots, and use row cover or a barrier to keep the flies off. In cold regions like the Upper Midwest and the Northeast, the long season and hard frosts actually work in your favor, since parsnips left in the ground into winter turn sweetest; in mild-winter areas, a late-summer sowing gives roots to dig through the cool months.

Parsnips grow slowly, so they pair well with plants that draw pollinators, lure away root pests, or cover the soil while the roots develop. These three make good neighbors for a parsnip row, and you can add any of them in one click:

Parsnips are ready in late fall, about 100 to 120 days after sowing, and they are one crop that is genuinely better for the wait. Leave the roots in the ground until after a hard frost or two, which turns their starches to sugar and makes them sweet and nutty. Loosen the soil deeply with a fork before lifting, since the roots run long and snap easily. You can keep digging them through winter under a straw mulch, but lift the last of them before they start to regrow in spring.

Parsnips are at their best roasted, when their sugars caramelize into something sweet, nutty, and golden. Roast them with other root vegetables, mash them like potatoes, or simmer them into soups and winter stews where they add body and a gentle sweetness. They pair well with butter, honey, and warm spices, and a frost-sweetened parsnip needs little more than a hot oven to shine.

• Seeds that never come up: old seed or a dried-out seedbed. Use fresh seed each year and keep the surface constantly moist for the 2 to 3 weeks it takes to germinate.
• Forked or twisted roots: stones, fresh manure, or transplanting. Dig a deep, stone-free bed, avoid fresh manure, and always direct-sow.
• Tunnels in the roots: carrot rust fly larvae. Cover the row with insect netting or a low barrier to keep the flies from laying eggs.
• Split roots: uneven watering, especially a heavy soak after dry soil. Water steadily so the roots grow at an even pace.