Marigold Companion Planting: What to Plant With Marigolds (and What They Really Do)

Marigolds are probably the most famous companion plant of all. They are cheap, easy from seed, bloom all summer and look cheerful at the end of a tomato row. They also come with a lot of folklore about repelling pests. This guide sorts out what extension sources actually list, what the research says marigolds do and do not do, and how to use them, including the right way to grow them if nematodes are your problem. Our companion planting for pest control guide shows which pest claims have research behind them.

Good companion plants for marigolds

Tomatoes

Virginia Extension lists marigolds as tomato companions and uses marigold, zinnia and tomato as an example of companion planting. French marigolds stay compact, so a few at the ends of a tomato row or at the corners of the bed take little space and do not shade anything. See what to plant with tomatoes.

Potatoes and eggplant

Both are listed with marigolds. Potatoes need hilling, so keep marigolds at the row ends rather than in the hills. Eggplant, a heat lover, goes out at about the same time as marigolds, after the soil warms. See what to plant with potatoes and what to plant with eggplant.

Squash, zucchini and pumpkins

Marigolds are listed with squash and with pumpkins. Sprawling vines can bury small plants, so put marigolds on the outside edge of the patch or between hills where the vines have not reached yet. See what to plant with zucchini and what to plant with pumpkins.

What not to plant with marigolds

None of the extension sources we use list a vegetable as incompatible with marigolds, so we do not show a keep-apart table here. Two practical cautions:

• Tall African marigolds can shade small crops. Clemson Extension notes African types can reach about 3 feet; use compact French marigolds next to low crops.
• Marigolds are not pest-proof. Clemson lists spider mites, slugs, aphids, whiteflies and thrips among the insects that can show up on marigolds, despite their reputation for repelling pests.

For pairs that sources do list as incompatible, see the keep-apart chart.

What marigolds really do: nematodes

Root-knot nematodes are microscopic worms that feed on roots and cause swellings, or galls, on the roots of many vegetables. University of Florida Extension explains that living marigold roots release a compound called alpha-terthienyl, and that marigolds can suppress root-knot and lesion nematodes. The details matter:

• Variety matters. UF/IFAS lists French marigold (Tagetes patula) varieties such as Single Gold and Tangerine as resistant to common root-knot nematodes. Signet marigolds such as Tangerine Gem and Golden Gem are listed as susceptible, which means they can make the problem worse.
• Interplanting does not do much. UF/IFAS says intercropping marigolds with susceptible crops probably does not reduce nematodes, and Clemson says intercropping for nematode control is not effective in protecting nearby plants. Nematodes simply feed on the vegetable roots next door.
• It works as a cover crop. Plant marigolds densely, in the exact spot where the vegetables will go, at least two months before the vegetable crop, then work them into the soil.
• It is not a cure. Marigolds suppress nematodes rather than eliminate them, and UF/IFAS notes they must be grown again each season to keep the effect. Some other nematode types can actually increase on marigolds.

How to use marigolds as a nematode cover crop

1. Confirm the problem.

   Galls on the roots of pulled plants are the classic sign. UF/IFAS recommends a nematode test through your extension office so you know which nematodes you have.

2. Choose a resistant variety.

   French marigolds Single Gold and Tangerine are the varieties both UF/IFAS and Clemson name; skip signet types.

3. Plant densely.

   UF/IFAS cites spacing of less than 7 inches between plants and rows, and keeping weeds out, because nematodes can multiply on weeds.

4. Grow them at least two months.

   Warm-season growth is when marigolds work best, so this suits a spring or summer slot before a fall crop, or a season off for a problem bed.

5. Turn them in, then plant.

   Hoe or dig the marigolds into the soil and plant your vegetables in the same spot. Repeat the next season if nematodes were bad.

How to grow marigolds

• When: Clemson Extension says to plant after the last spring frost. Start seeds indoors at 70°F to 75°F about four to six weeks ahead (about eight weeks for African types), or sow directly once the soil warms, about ¼ inch deep; seeds sprout in five to seven days. Our planting calendar helps you find your frost date.
• Spacing: French marigolds 8 to 10 inches apart; African marigolds 12 to 16 inches apart (closer for a nematode cover crop, as above).
• Sun and soil: full sun (six or more hours) and well-drained soil.
• Water: keep the soil evenly moist for the first couple of weeks until plants are established, then give about an inch a week.
• Care: remove faded flowers for more blooms, and stake tall African types if needed.

French, African, signet and pot marigolds

French marigolds (T. patula) are compact, bushy plants, while African marigolds (T. erecta) are bigger, with large blooms; Clemson Extension notes some reach about 3 feet. Signet marigolds have lacier leaves and small single flowers. Pot marigold (Calendula) is not a true marigold at all, so nematode advice for Tagetes does not apply to it. For a vegetable garden, compact French marigolds are the easiest companions. They are one of the aster-family flowers in our beneficial insect flower guide.

A simple tomato bed with marigolds

1. Tomatoes down the middle of a 4×8 bed.

   Caged or staked, about 2 feet apart.

2. French marigolds at the four corners and row ends.

   A listed tomato companion that stays low.

3. Basil between the tomato cages.

   Another listed tomato companion.

4. Potatoes in a different bed.

   Potatoes like marigolds too, but potatoes and tomatoes are listed as incompatible with each other.

Our raised bed layouts have more plans by the square foot.

Frequently asked questions

What grows well with marigolds?

Extension-listed companions for marigolds in our checker are eggplant, potatoes, pumpkins, squash (including zucchini) and tomatoes. The table on this page explains why each pairing works.