Fennel

Foeniculum vulgare

Apiaceae

Tomato

Solanum lycopersicum

Solanaceae

Can you plant fennel and tomatoes together?

Yes. Garden charts say to keep tomatoes away from fennel, but the tests we found say otherwise. A shared bed gave about 133% more harvest than separate beds in one field trial, and tomatoes had less disease next to fennel in a field trial.

Why the tests and the charts disagree

More harvest from the same bed. In one field trial, a bed with both crops gave about 133% more harvest than the same space split into a fennel bed and a tomato bed.
Produtividade do tomateiro em cultivo solteiro e consorciado com espécies aromáticas e medicinais X1 - Yield of tomato in monocrop and intercropping with aromatics plants (Carvalho · 2009)
Less disease. In a field trial, tomatoes had less disease next to fennel.
Intercropping with aromatic plants enhances tomato productivity and disease resilience through elevating soil nutrients and enzyme activities. (Yu Y · 2026 · Pest management science)
No clear effect on soil and nutrients. In a greenhouse or pot trial, growing them together made no clear difference to soil and nutrients.
The intercropping partner affects arbuscular mycorrhizal fungi and Fusarium oxysporum f. sp. lycopersici interactions in tomato (Hage-Ahmed · 2013 · Mycorrhiza)
Garden charts advise against it. 1 garden chart entry says to keep them apart. It cites no source. Charts pass on gardening tradition; they are not tests.
List of companion plants (uncited entry) (Wikipedia)

What to plant with fennel and tomatoes

No plant in our data is a good neighbour of both fennel and tomatoes yet.

What to keep away from fennel and tomatoes

RosemaryWith tomatoes: Garden charts advise against it, not tested

The evidence in detail

For readers who want to dig in: every chart entry, study and yield trial behind the answer above, with the numbers.

Tradition, research and yield trials

Tradition

Bad

avoidgood

1 chart entry: 0 recommend, 1 advise against.

0 cited, 1 uncited.

Research

Good

avoidgood

2 papers found: 1 positive, 0 negative, 1 no effect.

disease suppressionnutrients / soil

auto-classified not reviewed by a person

Yield trial

Good

1.66

0.67

Fennel gains more. Partial LER is each crop's share of the yield it would give alone.

1 field trial. Published LERs lean high.

Myth busted

What happens above and below ground

Each animation illustrates a mechanism a study reported for this pair. Pick a card to focus on it.

Everything at once.

What is going on (3)

Pick a card to spotlight its animation in the scene.

Fennel TomatoFennel helps shield Tomato from disease, for example by interrupting spread or disturbing the insects that carry it.

Researchfield trial x1

Intercropping with aromatic plants enhances tomato productivity and disease resilience through elevating soil nutrients and enzyme activities. (Yu Y · 2026 · Pest management science)

Fennel Tomato No clear effectStudies looked for nutrients / soil from Fennel to Tomato and found no clear effect.

Tomato Fennel No clear effectStudies looked for nutrients / soil from Tomato to Fennel and found no clear effect.

Researchgreenhouse / pot trial x1

The intercropping partner affects arbuscular mycorrhizal fungi and Fusarium oxysporum f. sp. lycopersici interactions in tomato (Hage-Ahmed · 2013 · Mycorrhiza)

Fennel TomatoMedian land equivalent ratio 2.33 over 1 trial: growing them together gave 2.33 times the harvest of two separate plots of the same size.

Partial LERs (medians): Fennel 1.66 + Tomato 0.67. Range across treatments 2.33 to 2.33. Medians are taken separately, so the parts need not add up to the median LER. LER above 1 is biased upward by publication bias.

Yield trialfield trial x1

Produtividade do tomateiro em cultivo solteiro e consorciado com espécies aromáticas e medicinais X1 - Yield of tomato in monocrop and intercropping with aromatics plants (Carvalho · 2009)

Tradition saysBad

1 gardening-lore entry, 1 without a specific citation. Lore is a starting point, not proof.

None of the 1 tradition entry cites a specific source.

Companion plants for both fennel and tomatoes

Plants that are good neighbours of each. Biggest harvest gain first; each cell links to the evidence for that pair.

No plant is a good neighbour of both fennel and tomatoes in our data yet.

The evidence, with sources

ResearchGood2 entries

Gooddisease suppressionfield trialauto-classified

Fennel helps Tomato
Intercropping with aromatic plants enhances tomato productivity and disease resilience through elevating soil nutrients and enzyme activities.
Intercropping with aromatic plants enhances tomato productivity and disease resilience through elevating soil nutrients and enzyme activities. (Yu Y · 2026 · Pest management science)

Relevance 90% · effect confidence 57%
No effectnutrients / soilgreenhouse / pot trialauto-classified

The intercropping partner affects arbuscular mycorrhizal fungi and Fusarium oxysporum f. sp. lycopersici interactions in tomato.
The intercropping partner affects arbuscular mycorrhizal fungi and Fusarium oxysporum f. sp. lycopersici interactions in tomato (Hage-Ahmed · 2013 · Mycorrhiza)

Relevance 95% · effect confidence 59%

Yield trialGood1 entry

GoodLER 2.33field trial

Brazil, 2006; Additive design; median LER 2.33 over 1 treatment(s) · partial LER Fennel 1.66, Tomato 0.67
Produtividade do tomateiro em cultivo solteiro e consorciado com espécies aromáticas e medicinais X1 - Yield of tomato in monocrop and intercropping with aromatics plants (Carvalho · 2009)

TraditionBad1 entry

Badadvises against
Tomatoes: avoid fennel
List of companion plants (uncited entry) (Wikipedia)

Plan a bed with fennel and tomatoes

All neighbours of fennel and of tomato, or every pair at once in the companion planting chart.

Have you grown fennel and tomatoes together?

Tell other gardeners what happened: spacing, pests, harvest, or ask a question. Reader notes are not checked by us and do not change the verdicts on this page.