Sweet Potato Companion Plants
Ipomoea batatas · morning glory family family · rotation group: other
The best companion plants for sweet potato are French Marigold (Tagetes patula), Sunn Hemp, Daikon Radish, Cereal Rye, and Bush Bean. Avoid planting sweet potato near Field Pea, Signet Marigold (Tagetes tenuifolia), Potato. Of the 11 pairings recorded here, 6 are supported by published research and 5 are traditional practice with no controlled evidence behind them.
What to plant with sweet potato
| Plant | Claimed benefit | Evidence | What the evidence actually shows |
|---|---|---|---|
| Cereal Rye | A winter cover crop of cereal rye with crimson clover, turned down before planting, suppresses early-season weeds in sweet potato. | Research-backed | Werle et al. (2023) found weed biomass lower in cover-cropped plots than bare soil at one of two Arkansas sites, and cover crop biomass correlated positively with several yield grades. Weed interference itself cut sweet potato yield 60-80%, so weed control matters far more than any decorative companion. Single-year, two-site trial. |
| Daikon Radish | Daikon radish grown as a winter cover crop before sweet potato keeps root-knot nematode populations low. | Research-backed | In the same 2025 Journal of Nematology screening, daikon radish and elbon rye were poor hosts and supported minimal M. incognita reproduction, and winter grasses plus daikon radish in mixes suppressed populations best. Evidence is greenhouse/microplot, and the benefit comes from the rotation slot, not from radishes growing alongside the crop. |
| French Marigold (Tagetes patula) | A solid stand of French marigold grown as a cover crop before sweet potato reduces root-knot nematode populations in the soil. | Research-backed | Real but narrow: UF/IFAS reports Tagetes suppresses root-knot (Meloidogyne) and lesion (Pratylenchus) nematodes, but only as a dense solid planting held at least two months before the crop, repeated every season; it states outright that 'intercropping marigold with other crops to reduce plant-parasitic nematodes does not appear to be effective' and that marigold raises stubby-root, sting, spiral and awl nematode numbers. Scattering a few marigolds among sweet potato slips does nothing. |
| Sunn Hemp | A summer cover crop of sunn hemp or velvetbean ahead of sweet potato lowers southern root-knot nematode pressure. | Research-backed | Schloemer et al. (2025) screened summer cover crops against Meloidogyne incognita on sweetpotato; velvetbean cut nematode populations roughly 94% relative to elbon rye and sunn hemp was among the poorest hosts. Limits: greenhouse and microplot only, not replicated field-scale sweet potato yield trials, and sunn hemp must be terminated before the crop rather than intercropped. |
| Borage | Borage is said to attract pollinators and predatory insects to the sweet potato patch. | Traditional | Untested for this crop. Sweet potato is harvested for roots and needs no insect pollination at all, so the pollinator half of the claim is irrelevant here; any benefit would have to come through generalist predators, which nobody has measured in sweet potato. |
| Bush Bean | Bush beans are said to fix nitrogen alongside young sweet potato vines and use the space before the canopy closes. | Traditional | No trial located. The mechanism also cuts against itself: sweet potato is deliberately grown on low nitrogen so it makes storage roots rather than vine, and its own canopy closes fast enough to shade out most weeds (Penn State), which means it will shade out a low legume too. |
| Dill | Flowering dill nearby is said to draw parasitoids and predators that reduce caterpillars feeding on sweet potato foliage. | Traditional | Flowering insectary plants do raise natural-enemy numbers as a general principle, but UMN Extension's review of companion planting finds most such pairings unsupported by crop-specific research, and no sweet potato trial was located. Foliage caterpillars rarely affect storage root yield anyway. |
| Nasturtium | Nasturtium is said to act as a trap plant pulling aphids and beetles off sweet potato. | Traditional | UMN Extension notes nasturtium with squash is supported by research showing reduced squash bug populations, but that result does not transfer: no equivalent work exists for sweet potato, whose main pests are soil-dwelling weevils, wireworms and nematodes that a trap flower cannot influence. |
What not to plant with sweet potato
| Plant | Claimed problem | Evidence | What the evidence actually shows |
|---|---|---|---|
| Field Pea | Field pea is often suggested as a soil-building winter legume, but planting it immediately before sweet potato makes root-knot nematode damage worse. | Research-backed | Schloemer et al. (2025) found field pea supported significantly more Meloidogyne incognita per gram of root than any other winter cover crop tested, with a reproductive factor of 15.3 — it multiplies the nematode fifteenfold right before a highly susceptible crop. Greenhouse and microplot data. |
| Signet Marigold (Tagetes tenuifolia) | Signet marigold planted for nematode control actually feeds the nematode instead. | Research-backed | UF/IFAS advises that signet marigolds should be avoided because nematodes will feed and reproduce on them, and notes that interplanting marigold with a susceptible crop is 'very risky'. Species and cultivar choice matters more than the plant simply being a marigold. |
| Potato | White potato is traditionally kept out of the sweet potato bed. | Traditional | The usual reason given (shared family) is simply wrong — potato is Solanaceae and sweet potato Convolvulaceae. There is a real but untested overlap: UC IPM notes root-knot nematode has a very wide vegetable host range and that the most reliable management is preventive rotation, so stacking two susceptible root crops raises pressure. Nobody has tested the pairing itself. |
The honest verdict
Of everything gardeners recommend planting alongside sweet potato, 4 pairings have been tested properly: French Marigold (Tagetes patula), Sunn Hemp, Daikon Radish, Cereal Rye. Those are the ones worth planning your bed around.
The remaining 4 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.
Every row above links to the publication it came from. See how we grade evidence.
Growing sweet potato: the numbers
| Sun | Full sun (6+ hours) |
|---|---|
| Water | Moderate |
| Spacing | 12 in apart · 36 in between rows · 1 per square foot |
| Mature size | about 12 in tall |
| Soil pH | 5.5–6.5 |
| Days to maturity | 90–120 days |
| Frost tolerance | Tender — killed by frost |
| Containers | Yes — 10 gallon minimum |
| Typical yield | about 2 lb of storage roots per hill |
| Common pests | sweetpotato weevil, root-knot nematode, wireworm, white grub, voles, deer |
| Common diseases | scurf, soil pox |
When to plant sweet potato
Zone 6b shownStart seeds indoors: Feb 13 – Feb 27 — 6–8 weeks before your last frost
Transplant outdoors: May 1 – May 14 — 3 weeks after last frost
Expected harvest: Jul 30 – Aug 29 — 90–120 days from planting
Those dates are for zone 6b. Get your own dates by ZIP code →
Varieties worth knowing
slips- Beauregard — 95-105 days; high-yielding and disease resistant, the leading commercial and home-garden standard. Note that all sweet potatoes are grown from slips (rooted sprouts pulled from a stored root), never from seed.
- Covington — 110-120 days; high-yielding with excellent flavor; NC State reports it tolerates Meloidogyne incognita but is highly susceptible to M. enterolobii.
- Vardaman — Bush-type vine rather than a long runner; Penn State lists it as one of the varieties that can be grown successfully in containers.
- Porto Rico — 110 days; compact vines with big yields and good baking quality, the other classic bush type for small gardens and containers.
Variety names link to slips 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 sweet potato 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 (other) — don't follow one with another:
Sweet Potato companion planting questions
What should not be planted next to sweet potato?
How far apart should sweet potato be planted?
Does companion planting with sweet potato actually work?
When should I plant sweet potato?
Sources for this record
- Mississippi State University Extension — Growing Sweet Potatoes at Home
- Penn State Extension — Sweet Potatoes, a Winning Vine for Your Garden
- University of Missouri Extension G6368 — Growing Sweet Potatoes in Missouri
- UGA Extension C1014 — Home Garden Sweet Potatoes
- UNH Extension — Growing Sweetpotatoes in New Hampshire
Record compiled 2026-07. Spot an error or a study we missed? Tell us and we'll correct the entry.