Parsnip Companion Plants
Pastinaca sativa · carrot family family · rotation group: root
The best companion plants for parsnip are Onion, White Clover (undersown living mulch), Radish, Leek, and Lettuce. Avoid planting parsnip near Carrot, Celery, Fennel. Of the 13 pairings recorded here, 3 are supported by published research and 9 are traditional practice with no controlled evidence behind them.
What to plant with parsnip
| Plant | Claimed benefit | Evidence | What the evidence actually shows |
|---|---|---|---|
| Onion | Onions intercropped with parsnip reduce carrot rust fly damage. | Research-backed | The strongest-evidenced pairing in this crop: UMass Extension's New England guide states outright that intercropping with onion has been shown to reduce carrot rust fly damage, backed by Uvah and Coaker's mixed-cropping work, but the effect scales with onion density and fades once the onions stop actively growing, so a token row of onions should not be expected to do much. |
| White Clover (undersown living mulch) | A low non-host groundcover between parsnip rows disrupts carrot rust fly host-finding. | Research-backed | Rämert and Ekbom's replicated field study found carrot rust fly damage was consistently lower under intercropping and traced it to the resource concentration effect rather than to predators, so any low green cover, not clover specifically, is doing the work; the trade-off is competition for water and nitrogen. |
| Bush Bean | Bush beans occupy the space between parsnip rows without competing for root depth. | Traditional | Different rooting depths make this workable, but no controlled trial demonstrates a yield benefit to either crop. |
| Leek | Leeks give the same allium intercrop protection against carrot rust fly as onions. | Traditional | Plausible by extension from the onion intercropping trials, but leeks specifically were not the crop tested, and leeks grow more slowly and at lower density than the onion plantings that produced the measured effect. |
| Lettuce | Lettuce is harvested long before parsnips size up, using the bed while the slow crop develops. | Traditional | A real intercropping efficiency given parsnip's 110-130 day season, but a scheduling benefit rather than a biological one. |
| Pea | Peas fix nitrogen and are cleared early, leaving the bed for the long parsnip season. | Traditional | Legume nitrogen fixation is well established, but most fixed nitrogen is removed with the crop rather than passed to a neighbor during the same season. |
| Radish | Radish sown along the parsnip furrow marks the slow-germinating row and breaks soil crust. | Traditional | Illinois Extension explicitly recommends this technique, so it is more than folklore as a cultural practice, but the benefit is mechanical row-marking and crust-breaking rather than any pest or growth interaction, and it has not been trial-quantified. |
| Sweet Alyssum | Alyssum flowers feed hoverflies and parasitoids that suppress aphids around the parsnip bed. | Traditional | Alyssum's value as an insectary plant is well supported in commercial lettuce systems, but I found no trial testing it in parsnip or against carrot rust fly, so the transfer is an assumption. |
| Tomato | Tomatoes shade the soil over parsnip roots through midsummer heat. | Traditional | Commonly recommended, never tested; in practice the shade is as likely to slow parsnip root sizing as to help it. |
What not to plant with parsnip
| Plant | Claimed problem | Evidence | What the evidence actually shows |
|---|---|---|---|
| Carrot | Carrots and parsnips grown together or in succession build up shared root pests. | Research-backed | Well supported as a rotation rule: carrot rust fly and carrot weevil overwinter in the soil and attack both hosts, and UMass Extension specifically advises rotating carrot and parsnip crops to new ground to escape overwintering adults. |
| Celery | Celery shares parsnip's family and concentrates the same pests and diseases. | Traditional | The shared-family rationale is sound and matches extension rotation advice for Apiaceae, but no study has measured a penalty from growing the two side by side in a garden. |
| Fennel | Fennel exudes compounds that inhibit neighboring vegetables including parsnip. | Traditional | Fennel allelopathy has been demonstrated in laboratory germination assays, but no field study shows a measurable effect on parsnip at garden spacing; fennel also hosts the same swallowtail caterpillars, which is a more concrete reason to separate them. |
| Dill | Dill cross-pollinates with parsnip and ruins the roots. | Not supported | Botanically impossible: dill is Anethum graveolens and parsnip is Pastinaca sativa, different genera that cannot cross, and in any case cross-pollination would only affect seed, never the root you harvest in year one. |
The honest verdict
Of everything gardeners recommend planting alongside parsnip, 2 pairings have been tested properly: Onion, White Clover (undersown living mulch). Those are the ones worth planning your bed around.
The remaining 7 pairings on this page are traditional practice. They circulate on every companion planting chart online, but we could not find controlled evidence testing them. They are not wrong so much as unverified — most cost nothing to try, and interplanting flowers and herbs has its own well-documented benefit of pulling pollinators and predatory insects into the garden.
Widely repeated, not supported: Dill — Botanically impossible: dill is Anethum graveolens and parsnip is Pastinaca sativa, different genera that cannot cross, and in any case cross-pollination would only affect seed, never the root you harvest in year one.
Every row above links to the publication it came from. See how we grade evidence.
Growing parsnip: the numbers
| Sun | Full sun (6+ hours) |
|---|---|
| Water | Moderate |
| Spacing | 4 in apart · 20 in between rows · 9 per square foot |
| Mature size | about 24 in tall |
| Soil pH | 6.2–7.2 |
| Days to maturity | 110–130 days |
| Frost tolerance | Hardy — takes hard frost |
| Containers | Yes — 5 gallon minimum |
| Typical yield | 1 root, 8-12 in long |
| Common pests | carrot rust fly, carrot weevil, aster leafhopper, cutworm, wireworm, swallowtail caterpillar |
| Common diseases | aster yellows, cavity spot, canker |
When to plant parsnip
Zone 6b shownDirect sow outdoors: Mar 27 – Apr 9 — 2 weeks before last frost
Expected harvest: Jul 15 – Aug 4 — 110–130 days from planting
Those dates are for zone 6b. Get your own dates by ZIP code →
Varieties worth knowing
seeds- Harris Model — long-standing smooth white main-crop standard, roughly 120 days
- All American — shorter, broad-shouldered roots that lift more easily from heavy ground
- Gladiator — vigorous hybrid with more reliable germination than open-pollinated types, about 110 days
- Hollow Crown — heirloom with long tapering roots; needs deep, stone-free soil
Variety names link to seeds on Amazon. As an Amazon Associate we earn from qualifying purchases. These are the varieties named in the extension sources for this crop, not a paid placement — where a source recommended a variety for a specific reason, that reason is the note beside it.
Put it in a bed
The garden planner checks every square against this ledger as you place crops — if you drop parsnip next to something recorded as a bad neighbour, the square turns red and tells you why.
Records for the plants named above:
Same rotation group (root) — don't follow one with another:
Parsnip companion planting questions
What should not be planted next to parsnip?
How far apart should parsnip be planted?
Does companion planting with parsnip actually work?
When should I plant parsnip?
Sources for this record
- Growing carrots and parsnips in home gardens — University of Minnesota Extension
- Parsnip — Illinois Extension Home Vegetable Gardening
- Growing Carrots and Parsnips — Iowa State University Extension Yard and Garden
- Carrot and Parsnip — New England Vegetable Management Guide, UMass Extension
- Parsnip — Texas A&M AgriLife Extension Vegetable Resources
Record compiled 2026-07. Spot an error or a study we missed? Tell us and we'll correct the entry.