How to Grow Parsnips

The germination trap: fresh seed, shallow sowing, long wait

Parsnip seed is very short-lived — it loses germination ability after the first year, so last spring's packet is the most common cause of an empty row. Buy fresh seed every year and discard leftovers.

Even fresh seed is slow: Utah State Extension says 14 to 21 days to emerge, with germination best at soil temperatures of 55 to 65°F. Sow two to three weeks before the last frost, shallowly (USU says 1/4 inch; Illinois Extension sows 1/2 to 3/4 inch deep), and thickly — two or three seeds per inch — because stand losses are expected.

Keep the seedbed evenly moist and unencrusted for those three weeks; a crusted or dried surface during the long germination window is the other classic way the crop fails. Some gardeners mark the row with a few fast radish seeds so they do not give up on it.

A full-season crop

Once up, thin to 3 to 6 inches apart in rows 12 to 18 inches apart (Illinois allows 8 to 10 inches between plants in beds) and treat parsnips like carrots that need twice the patience: deep, loose, stone-free soil grows straight roots, and the crop occupies the row for roughly 100 to 120 days.

There is no point rushing them out of the ground in summer — the flavor payoff comes later. Water steadily, keep them weeded early, and otherwise leave them alone until fall.

Frost sweetening and winter harvest

Cold is the seasoning: after exposure to near-freezing temperatures for two to four weeks, the starch in the root changes into sugar, giving parsnips their sweet, nutty flavor. Utah State Extension likewise says parsnips taste best after several weeks of cool, frosty weather — so harvest after hard frosts, not before.

You can also leave roots in the ground all winter: cover the crowns with a few inches of soil or straw mulch after the first fall frosts, and dig in early spring, when the roots are especially tender and sweet. Harvest before new leaf growth begins, because regrowing roots turn fibrous and lose flavor.

Dug roots store at 32°F and high humidity for a few weeks, or for months packed in moist sand in a cool cellar — but keep them away from apples and pears, whose ethylene makes parsnips bitter.

Sources

Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.

• Utah State University Extension — How to Grow Parsnips in Your Garden — Parsnips lose germination and seedling vigor rapidly after one year; germinate best at 55-65°F taking 14-21 days to emerge; sow 1/4 inch deep 2-3 weeks before last frost; thin to 3-6 inches in rows 12-18 inches apart; mature in 100-120 days; taste best after several weeks of cool, frosty weather; can overwinter in soil with a few inches over the crowns; store at 32°F and 95% humidity or in moist sand; keep away from apples/pears to avoid bitterness.
• Illinois Extension — Parsnip (Home Vegetable Gardening) — Parsnip seed is very short-lived and loses the ability to germinate after the first year — discard unused seed; seeds germinate very slowly even in the best conditions; sow 1/2 to 3/4 inch deep, 2-3 seeds per inch, rows 18-24 inches apart or 8-10 inches between plants in beds; after 2-4 weeks of near-freezing temperatures starch changes to sugar; overwintered roots are covered with soil or straw mulch and spring-harvested roots are especially tender and sweet if dug before new growth begins.

Keep going