Sources Library
Every source, with the claims it supports. A bibliography at the bottom of a page is not enough; the claim-to-source link is what you can check.
- journalfield2009
Bomford, M. K. (2009). Do tomatoes love basil but hate Brussels sprouts? Competition and land-use efficiency of popularly recommended and discouraged crop mixtures in biointensive agriculture systems.
Journal of Sustainable Agriculture · DOI 10.1080/10440040902835001 · Accessed 2026-08-21 · Scope: West Virginia, USA · Methods: Replicated field trials of crop mixtures at several densities; land equivalent ratio.
What it supports here. Tomato–basil mixtures achieved land-use efficiency above sole crops at some densities, while the popularly discouraged tomato–Brussels sprout mixture did not behave as a harmful pairing. Neither result depended on a special 'friendship'; density and competition explained the outcomes.
4 relationship records cite this source
- Basil ↔ Tomato: Conditional · In replicated field trials, tomato–basil mixtures used land more efficiently than either crop alone at some pl…
- Basil → Tomato: Traditional · Gardeners widely report that basil improves tomato flavour or growth. The reviewed field study measured yields…
- Brussels sprouts ↔ Tomato: Conflicting · Popular charts say tomatoes and Brussels sprouts (and other brassicas) should not be grown together. In the sa…
- Tomato ↔ Cabbage: Traditional · Tomatoes and cabbage-family crops are traditionally kept apart. The one field test of this tradition (tomato w…
Plant pages: Basil, Brussels sprouts
- journalfield2016
Brennan, E. B. (2016). Agronomy of strip intercropping broccoli with alyssum for biological control of aphids.
Biological Control · DOI 10.1016/j.biocontrol.2016.02.015 · Accessed 2026-08-21 · Scope: Salinas Valley, California, USA (organic field production) · Methods: Field trials of alyssum strips in organic broccoli.
What it supports here. Sweet alyssum strips supported hoverflies (syrphids) whose larvae eat aphids; the trade-off is land and competition, which can be minimised by planting alyssum in a small share of the bed.
3 relationship records cite this source
- Sweet alyssum → Broccoli: Conditional · Sweet alyssum strips in organic broccoli supported hoverflies whose larvae eat aphids; field agronomy showed t…
- Sweet alyssum → Kale: Conditional · By extension from broccoli and lettuce trials, alyssum near kale may support hoverflies that eat cabbage aphid…
- Sweet alyssum → Strawberry: Conditional · Alyssum attracts hoverflies whose larvae eat aphids; an effect on strawberry aphids is plausible but untested.…
Plant pages: Broccoli, Lettuce, Sweet alyssum
- journalfield2013
Brennan, E. B. (2013). Agronomic aspects of strip intercropping lettuce with alyssum for biological control of aphids.
Biological Control · DOI 10.1016/j.biocontrol.2013.03.017 · Accessed 2026-08-21 · Scope: Salinas Valley, California, USA (organic field production) · Methods: Field trials of alyssum interplanted in organic romaine lettuce at several ratios.
What it supports here. Replacing a small share of lettuce plants with alyssum supported hoverflies for aphid control; low alyssum ratios limited the loss of lettuce yield.
1 relationship record cite this source
- Sweet alyssum → Lettuce: Conditional · Alyssum strips interplanted with organic lettuce supported hoverflies for aphid biocontrol; the agronomy showe…
- journalsynthesis2015
Brooker, R. W., et al. (2015). Improving intercropping: a synthesis of research in agronomy, plant physiology and ecology.
New Phytologist · DOI 10.1111/nph.13132 · Accessed 2026-08-21 · Scope: Global synthesis · Methods: Review.
What it supports here. Intercrop productivity gains come from complementary use of light, water and nutrients in space and time, and from facilitation; gains are highest when the component crops differ in height, rooting depth or timing.
5 relationship records cite this source
- Tomato → Lettuce: Conditional · Lettuce bolts and scorches in summer heat; the partial shade cast by tomatoes on their east or north side can …
- Corn → Lettuce: Conditional · Corn casts deep shade to its north (in the northern hemisphere), which can keep summer lettuce cooler; in cool…
- Radish → Carrot: Conditional · Radishes sown in the same row as slow-germinating carrots mark the row, break the soil crust and are harvested…
- Carrot ↔ Lettuce: Conditional · Deep-rooted carrots and shallow-rooted lettuce use different soil layers and similar light, so they interplant…
- Peas → Lettuce: Conditional · Tall peas on netting cast light shade that can shelter late-spring lettuce as days warm; after the peas finish…
- meta analysissynthesis2023
Carrillo-Reche, J., et al. (2023). Cabbage intercropping synthesis (meta-analysis; title as cited in the project research brief).
Agriculture, Ecosystems & Environment · DOI 10.1016/j.agee.2023.108564 · Accessed 2026-08-21 · Scope: Global synthesis of cabbage intercropping trials · Methods: Meta-analysis of field trials.
What it supports here. Intercropping cabbage with companion plants substantially reduced pest injury on average, alongside a modest average reduction in cabbage productivity. These are trade-offs, not a free benefit.
The project brief cites this as the 2023 cabbage meta-analysis at AGEE 108564. Verify the full title and author list against the DOI before treating the citation as final.
3 relationship records cite this source
- White clover → Cabbage: Supported · Undersowing cabbage with white clover reduced egg-laying and infestation by several cabbage pests in replicate…
- White clover → Cabbage: Avoid · Unmanaged clover competes with cabbage for water and nutrients and reduced head size in field trials; the 2023…
- White clover → Broccoli: Conditional · The cabbage–clover pest-disruption effect is expected to transfer to broccoli (the same species, Brassica oler…
Plant pages: Cabbage, White clover
- journalfield2009
Cavanagh, A., Hazzard, R., Adler, L. S., Boucher, J. (2009). Using trap crops for control of Acalymma vittatum (Coleoptera: Chrysomelidae) reduces insecticide use in butternut squash.
Journal of Economic Entomology · DOI 10.1603/029.102.0319 · Accessed 2026-08-21 · Scope: Massachusetts and Connecticut, USA · Methods: On-farm trials of perimeter Blue Hubbard squash trap crops.
What it supports here. A perimeter of Blue Hubbard squash intercepted striped cucumber beetles arriving at butternut squash fields, reducing insecticide use when the trap crop itself was treated. The system requires the trap crop to be established before the main crop and managed.
2 relationship records cite this source
- Winter squash → Cucumber: Conditional · A perimeter of Blue Hubbard squash intercepted striped cucumber beetles arriving at butternut squash fields an…
- Winter squash → Zucchini: Conditional · Blue Hubbard squash at the perimeter can draw cucumber beetles away from summer squash, as shown for butternut…
Plant pages: Cucumber, Winter squash, Zucchini
- journalgreenhouse2019
Conboy, N. J. A., McDaniel, T., Ormerod, A., George, D., Gatehouse, A. M. R., Wharton, E., Donohoe, P., Curtis, R., Tosh, C. R. (2019). Companion planting with French marigolds protects tomato plants from glasshouse whiteflies through the emission of airborne limonene.
PLOS ONE · DOI 10.1371/journal.pone.0213071 · Accessed 2026-08-21 · Scope: UK glasshouse · Methods: Glasshouse experiments with interplanted French marigolds and limonene dispensers.
What it supports here. French marigolds interplanted with tomatoes reduced glasshouse whitefly numbers, and the effect was attributed to airborne limonene. The result was obtained in a glasshouse; outdoor effects may be weaker because volatiles disperse.
2 relationship records cite this source
- French marigold → Tomato: Conditional · French marigolds interplanted with tomatoes reduced glasshouse whitefly numbers in a UK glasshouse study; the …
- French marigold → Cabbage: Traditional · Marigolds are widely claimed to repel cabbage pests. The marigold evidence concerns glasshouse whitefly on tom…
Plant pages: French marigold
- journalsynthesis2007
Cook, S. M., Khan, Z. R., Pickett, J. A. (2007). The use of push-pull strategies in integrated pest management.
Annual Review of Entomology · DOI 10.1146/annurev.ento.52.110405.091407 · Accessed 2026-08-21 · Scope: Global review · Methods: Review.
What it supports here. Repellent ('push') and attractive ('pull') plants can be combined to manage pests, but documented systems are specific to named pests, plants and arrangements and were developed through field research rather than tradition.
- extensionguidance2024
Cornell University, Cornell Cooperative Extension (2024). Vegetable Growing Guides (Cornell Garden-Based Learning).
Cornell University · Accessed 2026-08-21 · Scope: New York, USA; temperate general · Methods: Extension growing guides.
What it supports here. Crop-by-crop guidance on sowing, transplanting, spacing, days to maturity, water and common problems used for catalog culture fields.
5 relationship records cite this source
- Tomato → Lettuce: Conditional · Lettuce bolts and scorches in summer heat; the partial shade cast by tomatoes on their east or north side can …
- Corn → Lettuce: Conditional · Corn casts deep shade to its north (in the northern hemisphere), which can keep summer lettuce cooler; in cool…
- Radish → Carrot: Conditional · Radishes sown in the same row as slow-germinating carrots mark the row, break the soil crust and are harvested…
- Carrot ↔ Lettuce: Conditional · Deep-rooted carrots and shallow-rooted lettuce use different soil layers and similar light, so they interplant…
- Peas → Lettuce: Conditional · Tall peas on netting cast light shade that can shelter late-spring lettuce as days warm; after the peas finish…
Plant pages: Arugula, Asparagus, Basil, Beet, Blueberry, Bok choy, Broccoli, Brussels sprouts, Bush beans, Cabbage, Carrot, Cauliflower, Celery, Collards, Corn, Cucumber, Eggplant, Garlic, Kale, Kohlrabi, Leek, Lettuce, Melon, Mustard greens, Okra, Onion, Parsley, Parsnip, Peas, Pepper, Pole beans, Potato, Pumpkin, Radish, Raspberry, Spinach, Strawberry, Sweet potato, Swiss chard, Tomato, Turnip, Winter squash, Zucchini
- journalsynthesis2015
Duke, S. O. (2015). Proving allelopathy in crop–weed interactions.
Weed Science · DOI 10.1614/WS-D-13-00130.1 · Accessed 2026-08-21 · Scope: Global review · Methods: Review of allelopathy methodology.
What it supports here. Laboratory and pot bioassays frequently overstate allelopathy; proving a field effect requires showing the chemical is released at active concentrations in soil and that competition has been excluded. Most popular allelopathy claims have not met that bar.
4 relationship records cite this source
- Florence fennel → Tomato: Traditional · Fennel is widely listed as inhibiting tomatoes and most other vegetables. Laboratory bioassays find inhibitory…
- Florence fennel → Bush beans: Traditional · Fennel is said to stunt beans. Only laboratory evidence of inhibitory compounds exists; field effects are unpr…
- Sunflower → Potato: Traditional · Sunflowers are said to inhibit potatoes and beans through allelopathy. Laboratory bioassays show inhibitory co…
- Sunflower → Pole beans: Traditional · Sunflowers are said to stunt beans. Laboratory evidence only; shading is the demonstrable problem.…
Plant pages: Florence fennel, Sunflower
- journalfield2000
Finch, S., Collier, R. H. (2000). Host-plant selection by insects – a theory based on 'appropriate/inappropriate landings' by pest insects of cruciferous plants.
Entomologia Experimentalis et Applicata · DOI 10.1046/j.1570-7458.2000.00684.x · Accessed 2026-08-21 · Scope: UK · Methods: Field and laboratory experiments on pest host-finding with background plants.
What it supports here. Non-host plants surrounding brassicas disrupted pest host-finding (inappropriate landings), reducing egg-laying by cabbage root fly and others. The effect depends on ground cover, not the identity of a 'repellent' companion.
2 relationship records cite this source
- White clover → Cabbage: Supported · Undersowing cabbage with white clover reduced egg-laying and infestation by several cabbage pests in replicate…
- White clover → Broccoli: Conditional · The cabbage–clover pest-disruption effect is expected to transfer to broccoli (the same species, Brassica oler…
Plant pages: Cabbage, White clover
- journalfield2011
Hogg, B. N., Bugg, R. L., Daane, K. M. (2011). Attractiveness of common insectary and harvestable floral resources to beneficial insects.
Biological Control · DOI 10.1016/j.biocontrol.2010.09.007 · Accessed 2026-08-21 · Scope: California, USA · Methods: Field observation of beneficial insect visits to flowering plants.
What it supports here. Sweet alyssum, coriander, buckwheat and some other small-flowered plants attracted hoverflies, parasitic wasps and other beneficials; attractiveness differed by plant and insect group, so 'flowers help beneficials' must be specific.
8 relationship records cite this source
- Sweet alyssum → Broccoli: Conditional · Sweet alyssum strips in organic broccoli supported hoverflies whose larvae eat aphids; field agronomy showed t…
- Sweet alyssum → Lettuce: Conditional · Alyssum strips interplanted with organic lettuce supported hoverflies for aphid biocontrol; the agronomy showe…
- Sweet alyssum → Kale: Conditional · By extension from broccoli and lettuce trials, alyssum near kale may support hoverflies that eat cabbage aphid…
- Sweet alyssum → Strawberry: Conditional · Alyssum attracts hoverflies whose larvae eat aphids; an effect on strawberry aphids is plausible but untested.…
- Dill → Cabbage: Conditional · Flowering dill is attractive to hoverflies, lacewings and parasitic wasps that attack cabbage pests; an effect…
- Cilantro → Cabbage: Conditional · Flowering coriander was among the plants most visited by hoverflies and parasitic wasps in field observations;…
- Buckwheat → Cabbage: Conditional · Buckwheat flowers are strongly attractive to hoverflies and parasitic wasps; a strip beside cabbage may suppor…
- Buckwheat → Cucumber: Conditional · Buckwheat supports hoverflies and parasitic wasps that may reduce aphids on cucumbers; plausible, untested on …
Plant pages: Buckwheat, Calendula, Chives, Cilantro, Cosmos, Dill, Florence fennel, Parsley, Sweet alyssum
- journalsynthesis1991
Hokkanen, H. M. T. (1991). Trap cropping in pest management.
Annual Review of Entomology · DOI 10.1146/annurev.en.36.010191.001003 · Accessed 2026-08-21 · Scope: Global review · Methods: Review.
What it supports here. Defines trap cropping and reviews its successes and failures; emphasises that trap crops must be more attractive than the main crop at the right time and must be managed to prevent the pest returning to the main crop.
- journalsynthesis2010
Hooks, C. R. R., Wang, K.-H., Ploeg, A., McSorley, R. (2010). Using marigold (Tagetes spp.) as a cover crop to protect crops from plant-parasitic nematodes.
Applied Soil Ecology · DOI 10.1016/j.apsoil.2010.09.005 · Accessed 2026-08-21 · Scope: Review, mainly USA · Methods: Literature review of marigold cover-crop and intercrop trials.
What it supports here. Marigolds suppress some root-knot nematodes mainly when grown as a dense cover crop before the susceptible crop; as an interplanted companion the effect is smaller and cultivar-dependent.
2 relationship records cite this source
- French marigold → Tomato: Conditional · Marigolds (Tagetes) suppress some root-knot nematodes, but mainly when grown as a dense cover crop for a seaso…
- French marigold → Carrot: Conditional · A dense marigold cover crop in the season before carrots can reduce root-knot nematodes that fork and gall car…
Plant pages: French marigold
- journalsynthesis2022
Huss, C. P., Holmes, K. D., Blubaugh, C. K. (2022). Benefits and risks of intercropping for crop resilience and pest management.
Journal of Economic Entomology · DOI 10.1093/jee/toac045 · Accessed 2026-08-21 · Scope: Global review · Methods: Narrative review of intercropping research.
What it supports here. Intercropping can reduce pest pressure and increase resilience, but outcomes depend on the specific combination; costs include competition, labour and management complexity.
- meta analysissynthesis2023
Kirsch, F., et al. (2023). Intercropping, beneficial arthropods, and pests (meta-analysis; title as cited in the project research brief).
Agriculture, Ecosystems & Environment · DOI 10.1016/j.agee.2023.108617 · Accessed 2026-08-21 · Scope: Global synthesis · Methods: Systematic review and meta-analysis of arthropod responses to intercropping.
What it supports here. Intercropping tends to increase beneficial arthropods and reduce pests on average, but the size and direction of effects vary considerably by crop combination and spatial arrangement.
The project brief cites this as the 2023 arthropod meta-analysis at AGEE 108617. The DOI is the claim-to-source link; the full title and author list must be verified against the DOI before the citation is treated as final.
- meta analysissynthesis2011
Letourneau, D. K., et al. (2011). Does plant diversity benefit agroecosystems? A synthetic review.
Ecological Applications · DOI 10.1890/09-2026.1 · Accessed 2026-08-21 · Scope: Global synthesis · Methods: Meta-analysis of 552 experiments.
What it supports here. Diversified cropping systems generally reduced herbivore pests and increased natural enemies compared with monocultures, with crop damage lower on average; yield responses were mixed.
2 relationship records cite this source
- journalfield2000
Mitchell, E. R., Hu, G., Johanowicz, D. (2000). Management of diamondback moth (Lepidoptera: Plutellidae) in cabbage using collard as a trap crop.
HortScience · DOI 10.21273/HORTSCI.35.5.875 · Accessed 2026-08-21 · Scope: Florida, USA · Methods: Field trials with collard perimeter rows around cabbage.
What it supports here. Collards planted around cabbage attracted diamondback moth egg-laying and reduced the need to spray the cabbage; the trap rows had to be maintained and treated.
1 relationship record cite this source
- journalfield2016
Mt. Pleasant, J. (2016). Food yields and nutrient analyses of the Three Sisters: a Haudenosaunee cropping system.
Ethnobiology Letters · DOI 10.14237/ebl.7.1.2016.721 · Accessed 2026-08-21 · Scope: New York, USA · Methods: Field plots comparing the Three Sisters polyculture with sole crops.
What it supports here. The corn–bean–squash polyculture produced more food energy and protein per area than the sole crops, through physical support, complementary canopies and ground cover; individual crop yields were lower than monocultures.
4 relationship records cite this source
- Corn → Pole beans: Supported · Corn stalks provide physical support for climbing beans; in measured Three Sisters plots the polyculture produ…
- Pole beans → Corn: Conditional · Beans fix nitrogen, but reviews show only a small, variable share reaches neighbouring corn during the season;…
- Winter squash ↔ Corn: Supported · Squash vines spread beneath corn and beans, shading the soil and suppressing weeds, while corn grows above; th…
- Pole beans ↔ Winter squash: Conditional · Climbing beans and sprawling squash occupy different layers; measured as part of the three-crop system, not as…
Plant pages: Corn, Pole beans, Winter squash
- governmentdataset2021
NOAA National Centers for Environmental Information (2021). U.S. Climate Normals (1991–2020).
NOAA NCEI · Accessed 2026-08-21 · Scope: USA · Methods: Station climate normals including frost probabilities.
What it supports here. Average frost dates used as starting estimates; actual frost varies by year and microclimate, which is why the calendar shows an uncertainty band and lets users confirm dates.
- extensionguidance2019
Oregon State University Extension Service (2019). Growing Your Own (EM 9027).
Oregon State University Extension · Accessed 2026-08-21 · Scope: Oregon, USA (Pacific Northwest) · Methods: Extension growing guide with planting dates, spacing and culture.
What it supports here. Region-specific planting dates, spacing and cultural requirements for common vegetables in western and eastern Oregon, used here for Pacific Northwest calendar assumptions.
- extensionguidance2025
Royal Horticultural Society (2025). Grow Your Own vegetables, herbs and fruit.
Royal Horticultural Society · Accessed 2026-08-21 · Scope: United Kingdom; temperate maritime · Methods: Horticultural society growing guides.
What it supports here. Cultivation guidance for cool-temperate maritime climates, including sowing months, spacing, support and container suitability.
3 relationship records cite this source
- Radish → Carrot: Conditional · Radishes sown in the same row as slow-germinating carrots mark the row, break the soil crust and are harvested…
- Tomato ↔ Strawberry: Avoid · Strawberries and tomatoes share Verticillium wilt, a soil-borne fungus. The main risk is planting strawberries…
- Potato ↔ Strawberry: Avoid · Potatoes and strawberries share Verticillium wilt; avoid planting strawberries in beds that grew potatoes in t…
Plant pages: Arugula, Asparagus, Basil, Beet, Blueberry, Bok choy, Borage, Broccoli, Brussels sprouts, Bush beans, Cabbage, Calendula, Carrot, Cauliflower, Celery, Chives, Cilantro, Cosmos, Cucumber, Dill, Eggplant, Florence fennel, Garlic, Kale, Kohlrabi, Lavender, Leek, Lettuce, Melon, Mint, Nasturtium, Onion, Oregano, Parsley, Parsnip, Peas, Pepper, Pole beans, Potato, Pumpkin, Radish, Raspberry, Rhubarb, Rosemary, Sage, Spinach, Strawberry, Sunflower, Swiss chard, Thyme, Tomato, Turnip, Zucchini
- journalsynthesis2006
Shelton, A. M., Badenes-Perez, F. R. (2006). Concepts and applications of trap cropping in pest management.
Annual Review of Entomology · DOI 10.1146/annurev.ento.51.110104.150959 · Accessed 2026-08-21 · Scope: Global review · Methods: Review of trap cropping theory and cases.
What it supports here. Successful trap cropping depends on the pest's preference, the trap crop's attractiveness over time, arrangement (usually perimeter), and on destroying pests in the trap crop; most failures come from ignoring one of these.
3 relationship records cite this source
- Collards → Cabbage: Conditional · Collards planted around cabbage attracted diamondback moth egg-laying and reduced the need to spray the cabbag…
- Mustard greens → Cabbage: Conditional · Mustard is used on farms as a perimeter trap crop for several brassica pests because it is more attractive tha…
- Nasturtium → Cabbage: Traditional · Nasturtiums are said to draw cabbage white butterflies and aphids away from brassicas. They are certainly colo…
Plant pages: Mustard greens, Nasturtium
- governmentguidance2009
Sustainable Agriculture Research and Education (SARE) (2009). Using trap crops to reduce pests (Crop Rotation on Organic Farms: Guidelines for intercropping).
SARE / USDA · Accessed 2026-08-21 · Scope: USA · Methods: Practitioner guidance synthesising research.
What it supports here. A trap crop works only when the pest clearly prefers it, it is planted earlier or at the perimeter where pests arrive, it is monitored, and the pests it collects are destroyed before they move to the main crop.
4 relationship records cite this source
- Collards → Cabbage: Conditional · Collards planted around cabbage attracted diamondback moth egg-laying and reduced the need to spray the cabbag…
- Mustard greens → Cabbage: Conditional · Mustard is used on farms as a perimeter trap crop for several brassica pests because it is more attractive tha…
- Winter squash → Cucumber: Conditional · A perimeter of Blue Hubbard squash intercepted striped cucumber beetles arriving at butternut squash fields an…
- Winter squash → Zucchini: Conditional · Blue Hubbard squash at the perimeter can draw cucumber beetles away from summer squash, as shown for butternut…
Plant pages: Collards, Cucumber, Mustard greens, Winter squash
- journalfield1995
Theunissen, J., Booij, C. J. H., Lotz, L. A. P. (1995). Effects of intercropping white cabbage with clovers on pest infestation and yield.
Entomologia Experimentalis et Applicata · DOI 10.1111/j.1570-7458.1995.tb01868.x · Accessed 2026-08-21 · Scope: Netherlands · Methods: Field trials of cabbage undersown with clover.
What it supports here. Undersowing cabbage with clover reduced several pests, but the clover competed with cabbage and reduced head size unless managed (for example by mowing or delayed sowing).
3 relationship records cite this source
- White clover → Cabbage: Supported · Undersowing cabbage with white clover reduced egg-laying and infestation by several cabbage pests in replicate…
- White clover → Cabbage: Avoid · Unmanaged clover competes with cabbage for water and nutrients and reduced head size in field trials; the 2023…
- White clover → Broccoli: Conditional · The cabbage–clover pest-disruption effect is expected to transfer to broccoli (the same species, Brassica oler…
Plant pages: Cabbage, White clover
- journalsynthesis2016
Thilakarathna, M. S., McElroy, M. S., Chapagain, T., Papadopoulos, Y. A., Raizada, M. N. (2016). Belowground nitrogen transfer from legumes to non-legumes under managed herbaceous cropping systems. A review.
Agronomy for Sustainable Development · DOI 10.1007/s13593-016-0396-4 · Accessed 2026-08-21 · Scope: Global review · Methods: Literature review of nitrogen transfer studies.
What it supports here. Living legumes transfer only a small and variable share of fixed nitrogen to neighbours during the season; most benefit comes after residues decompose. A legume next to a heavy feeder is not a fertiliser substitute.
1 relationship record cite this source
- Pole beans → Corn: Conditional · Beans fix nitrogen, but reviews show only a small, variable share reaches neighbouring corn during the season;…
Plant pages: Bush beans, Peas, Pole beans, White clover
- extensionguidance2025
University of California Statewide Integrated Pest Management Program (2025). Home, garden, turf and landscape pests.
UC Agriculture and Natural Resources · Accessed 2026-08-21 · Scope: California, USA; pest biology broadly applicable · Methods: IPM pest notes.
What it supports here. Pest biology and host ranges, including that corn earworm and tomato fruitworm are the same insect (Helicoverpa zea) and that late blight affects both potato and tomato.
3 relationship records cite this source
- Potato ↔ Tomato: Avoid · Potato and tomato are both hosts of late blight; spores spread readily between adjacent plants, and infected p…
- Corn ↔ Tomato: Avoid · Corn earworm and tomato fruitworm are the same moth. Moths emerging from corn move readily to adjacent tomatoe…
- Potato ↔ Eggplant: Avoid · Eggplant is a preferred host of Colorado potato beetle and shares soil-borne wilts with potato; adjacent plant…
- extensionguidance2023
University of Minnesota Extension (2023). Companion planting in home gardens.
University of Minnesota Extension · Accessed 2026-08-21 · Scope: Minnesota, USA; general home-garden guidance · Methods: Extension synthesis distinguishing research-backed examples from tradition.
What it supports here. Separates companion practices with research support (for example trap crops, insectary plants and physical support) from traditional pairings whose origins are hard to identify, and cautions that many popular charts are not evidence-based.
84 relationship records cite this source
- Basil → Tomato: Traditional · Gardeners widely report that basil improves tomato flavour or growth. The reviewed field study measured yields…
- Basil → Tomato: Traditional · Basil is commonly said to repel aphids, whitefly and hornworms from tomatoes. The review found no field trial …
- Brussels sprouts ↔ Tomato: Conflicting · Popular charts say tomatoes and Brussels sprouts (and other brassicas) should not be grown together. In the sa…
- Corn → Pole beans: Supported · Corn stalks provide physical support for climbing beans; in measured Three Sisters plots the polyculture produ…
- Onion → Carrot: Conditional · In UK field trials, carrot fly damage fell only when onions greatly outnumbered carrots (about four onion rows…
- Potato ↔ Tomato: Avoid · Potato and tomato are both hosts of late blight; spores spread readily between adjacent plants, and infected p…
- Corn ↔ Tomato: Avoid · Corn earworm and tomato fruitworm are the same moth. Moths emerging from corn move readily to adjacent tomatoe…
- Nasturtium → Cabbage: Traditional · Nasturtiums are said to draw cabbage white butterflies and aphids away from brassicas. They are certainly colo…
- Nasturtium → Bush beans: Traditional · Nasturtiums are said to lure black bean aphids away from beans. Nasturtiums are a favoured aphid host, but no …
- Nasturtium → Cucumber: Traditional · Nasturtiums are said to deter cucumber beetles and squash bugs. No controlled evidence was found; the document…
- French marigold → Cabbage: Traditional · Marigolds are widely claimed to repel cabbage pests. The marigold evidence concerns glasshouse whitefly on tom…
- French marigold → Bush beans: Traditional · Marigolds are said to deter Mexican bean beetle. No controlled evidence found.…
- Borage → Tomato: Traditional · Borage is said to deter tomato hornworm and improve tomato growth. No controlled evidence found. Borage flower…
- Borage → Strawberry: Traditional · Borage is said to improve strawberry flavour and yield and to attract pollinators. Bee visits are real; the fl…
- Borage → Zucchini: Traditional · Borage flowers are heavily visited by bumblebees and honeybees, which squash need for fruit set; whether borag…
- Basil → Pepper: Traditional · Basil is said to repel aphids and improve peppers, by extension from the tomato tradition. No pepper-specific …
- Chives → Carrot: Traditional · Chives and other alliums are said to deter carrot rust fly. The only field evidence is for onions at very high…
- Chives → Strawberry: Traditional · Chives are said to deter aphids and improve strawberry health. No controlled evidence found.…
- Garlic → Tomato: Traditional · Garlic is said to repel aphids and spider mites from tomatoes. No controlled evidence for interplanted garlic …
- Sage → Cabbage: Traditional · Sage is said to deter cabbage moths and carrot fly. No controlled evidence found. Sage also needs far drier so…
- Mint → Cabbage: Traditional · Mint is said to repel cabbage pests, ants and aphids. No controlled evidence found, and mint spreads aggressiv…
- Thyme → Cabbage: Traditional · Thyme is said to deter cabbage white butterflies. No controlled evidence found; thyme prefers much drier soil.…
- Rosemary → Carrot: Traditional · Rosemary is said to deter carrot rust fly. No controlled evidence found. Rosemary needs dry, lean soil unlike …
- Rosemary → Bush beans: Traditional · Rosemary is said to repel bean beetles. No controlled evidence found.…
- Radish → Cucumber: Traditional · Radishes are said to deter cucumber beetles. No controlled evidence found.…
- Bush beans → Potato: Traditional · Beans are said to deter Colorado potato beetle, and potatoes to deter Mexican bean beetle. No controlled evide…
- Carrot → Tomato: Traditional · A popular book title aside, no study shows that carrots improve tomatoes or vice versa. Carrots do fit beneath…
- Tomato ↔ Asparagus: Traditional · Tomatoes are said to deter asparagus beetle and asparagus to deter nematodes in tomatoes. No controlled eviden…
- Spinach ↔ Strawberry: Traditional · Spinach and strawberries are said to grow well together. They are both low and cool-season, so they coexist wi…
- Beet ↔ Onion: Traditional · Beets and onions are commonly listed as good neighbours. They have compatible needs and sizes; no benefit beyo…
- Cucumber → Sunflower: Traditional · Sunflowers are sometimes used as living trellises for cucumbers. Mechanically plausible, but sunflowers shade …
- Peas → Spinach: Traditional · Peas are said to shelter spinach. Light shade from peas can delay spinach bolting; this is a spatial fit rathe…
- Rhubarb → Cabbage: Traditional · Rhubarb is said to deter brassica pests, sometimes by using its leaves as a spray. No controlled evidence; rhu…
- Calendula → Tomato: Traditional · Calendula is said to deter tomato hornworm and aphids. No controlled evidence; calendula itself hosts aphids, …
- Lavender → Cabbage: Traditional · Lavender is said to repel cabbage moths. No controlled evidence; lavender needs dry, lean soil that cabbage wo…
- Oregano → Cucumber: Traditional · Oregano is said to repel cucumber beetles. No controlled evidence found.…
- Cosmos → Tomato: Traditional · Cosmos is said to attract beneficial insects that protect tomatoes. Cosmos flowers do feed hoverflies and bees…
- Florence fennel → Tomato: Traditional · Fennel is widely listed as inhibiting tomatoes and most other vegetables. Laboratory bioassays find inhibitory…
- Onion ↔ Bush beans: Traditional · Alliums and beans are traditionally listed as enemies, sometimes with the claim that onions inhibit bean growt…
- Garlic ↔ Peas: Traditional · Garlic and peas are traditionally listed as incompatible. No evidence found; garlic is lifted in early summer …
- Tomato ↔ Cabbage: Traditional · Tomatoes and cabbage-family crops are traditionally kept apart. The one field test of this tradition (tomato w…
- Dill → Tomato: Traditional · Mature, flowering dill is said to stunt tomatoes while young dill helps them. No controlled evidence for eithe…
- Pole beans ↔ Onion: Traditional · Climbing beans and onions are traditionally listed as incompatible. No controlled evidence found.…
- Kohlrabi ↔ Tomato: Traditional · Kohlrabi and tomatoes are traditionally said to stunt each other. No evidence found for either direction.…
- Tomato ↔ Cucumber: No verified relationship · We did not find a source that establishes a benefit or harm between tomato and cucumber.…
- Tomato ↔ Pepper: No verified relationship · We did not find a source that establishes a benefit or harm between tomato and pepper.…
- Pepper ↔ Eggplant: No verified relationship · We did not find a source that establishes a benefit or harm between pepper and eggplant.…
- Pepper ↔ French marigold: No verified relationship · We did not find a source that establishes a benefit or harm between pepper and marigold.…
- Tomato ↔ Zucchini: No verified relationship · We did not find a source that establishes a benefit or harm between tomato and zucchini.…
- Cucumber ↔ Bush beans: No verified relationship · We did not find a source that establishes a benefit or harm between cucumber and bush beans.…
- Peas ↔ Carrot: No verified relationship · We did not find a source that establishes a benefit or harm between peas and carrot.…
- Lettuce ↔ Strawberry: No verified relationship · We did not find a source that establishes a benefit or harm between lettuce and strawberry.…
- Onion ↔ Lettuce: No verified relationship · We did not find a source that establishes a benefit or harm between onion and lettuce.…
- Carrot ↔ Onion: No verified relationship · We did not find a source that establishes a benefit or harm between carrot and onion.…
- Potato ↔ Corn: No verified relationship · We did not find a source that establishes a benefit or harm between potato and corn.…
- Cucumber ↔ Melon: No verified relationship · We did not find a source that establishes a benefit or harm between cucumber and melon.…
- Zucchini ↔ Pumpkin: No verified relationship · We did not find a source that establishes a benefit or harm between zucchini and pumpkin.…
- Garlic ↔ Strawberry: No verified relationship · We did not find a source that establishes a benefit or harm between garlic and strawberry.…
- Spinach ↔ Peas: No verified relationship · We did not find a source that establishes a benefit or harm between spinach and peas.…
- Kale ↔ Onion: No verified relationship · We did not find a source that establishes a benefit or harm between kale and onion.…
- Beet ↔ Bush beans: No verified relationship · We did not find a source that establishes a benefit or harm between beet and bush beans.…
- Swiss chard ↔ Tomato: No verified relationship · We did not find a source that establishes a benefit or harm between swiss chard and tomato.…
- Broccoli ↔ Tomato: No verified relationship · We did not find a source that establishes a benefit or harm between broccoli and tomato.…
- Sweet potato ↔ Bush beans: No verified relationship · We did not find a source that establishes a benefit or harm between sweet potato and bush beans.…
- Okra ↔ Pepper: No verified relationship · We did not find a source that establishes a benefit or harm between okra and pepper.…
- Celery ↔ Cabbage: No verified relationship · We did not find a source that establishes a benefit or harm between celery and cabbage.…
- Parsley ↔ Tomato: No verified relationship · We did not find a source that establishes a benefit or harm between parsley and tomato.…
- Leek ↔ Carrot: No verified relationship · We did not find a source that establishes a benefit or harm between leek and carrot.…
- Blueberry ↔ Strawberry: No verified relationship · We did not find a source that establishes a benefit or harm between blueberry and strawberry.…
- Asparagus ↔ Parsley: No verified relationship · We did not find a source that establishes a benefit or harm between asparagus and parsley.…
- Lettuce ↔ Radish: No verified relationship · We did not find a source that establishes a benefit or harm between lettuce and radish.…
- Bok choy ↔ Cilantro: No verified relationship · We did not find a source that establishes a benefit or harm between bok choy and cilantro.…
- Turnip ↔ Peas: No verified relationship · We did not find a source that establishes a benefit or harm between turnip and peas.…
- Raspberry ↔ Garlic: No verified relationship · We did not find a source that establishes a benefit or harm between raspberry and garlic.…
- Rhubarb ↔ Strawberry: No verified relationship · We did not find a source that establishes a benefit or harm between rhubarb and strawberry.…
- Arugula ↔ Bush beans: No verified relationship · We did not find a source that establishes a benefit or harm between arugula and bush beans.…
- Mustard greens ↔ Onion: No verified relationship · We did not find a source that establishes a benefit or harm between mustard greens and onion.…
- Collards ↔ Onion: No verified relationship · We did not find a source that establishes a benefit or harm between collards and onion.…
- Cauliflower ↔ Celery: No verified relationship · We did not find a source that establishes a benefit or harm between cauliflower and celery.…
- Eggplant ↔ Bush beans: No verified relationship · We did not find a source that establishes a benefit or harm between eggplant and bush beans.…
- Winter squash ↔ Nasturtium: No verified relationship · We did not find a source that establishes a benefit or harm between winter squash and nasturtium.…
- Melon ↔ Corn: No verified relationship · We did not find a source that establishes a benefit or harm between melon and corn.…
- Parsnip ↔ Onion: No verified relationship · We did not find a source that establishes a benefit or harm between parsnip and onion.…
- Kohlrabi ↔ Beet: No verified relationship · We did not find a source that establishes a benefit or harm between kohlrabi and beet.…
Plant pages: Borage, French marigold, Mint, Nasturtium, Onion, Sage
- extensionguidance2023
University of Minnesota Extension (2023). Living soil, healthy garden: crop rotation and soil health.
University of Minnesota Extension · Accessed 2026-08-21 · Scope: Minnesota, USA; general · Methods: Extension synthesis.
What it supports here. Recommends rotating plant families between seasons to interrupt soil-borne disease and pest cycles, and explains how rotation differs from planting companions together.
Plant pages: Buckwheat
- extensionguidance2023
University of Minnesota Extension (2023). Managing plant diseases in the home garden.
University of Minnesota Extension · Accessed 2026-08-21 · Scope: USA; general · Methods: Extension synthesis.
What it supports here. Explains sanitation, rotation, spacing for airflow, resistant cultivars and watering practice as the core of home-garden disease management.
6 relationship records cite this source
- Potato ↔ Tomato: Avoid · Potato and tomato are both hosts of late blight; spores spread readily between adjacent plants, and infected p…
- Potato ↔ Eggplant: Avoid · Eggplant is a preferred host of Colorado potato beetle and shares soil-borne wilts with potato; adjacent plant…
- Tomato ↔ Strawberry: Avoid · Strawberries and tomatoes share Verticillium wilt, a soil-borne fungus. The main risk is planting strawberries…
- Potato ↔ Strawberry: Avoid · Potatoes and strawberries share Verticillium wilt; avoid planting strawberries in beds that grew potatoes in t…
- Tomato ↔ Raspberry: Avoid · Raspberries share Verticillium wilt with nightshades; do not establish a raspberry row where tomatoes or potat…
- Cucumber ↔ Potato: Traditional · Cucumbers and potatoes are traditionally kept apart, sometimes citing blight. Late blight of potato (Phytophth…
Plant pages: Cucumber, Potato, Strawberry, Tomato
- governmentdataset2023
USDA Agricultural Research Service (2023). USDA Plant Hardiness Zone Map.
USDA ARS · Accessed 2026-08-21 · Scope: USA · Methods: Climate mapping from average annual minimum temperature.
What it supports here. Zones describe average winter minimum temperature only; they are an input for perennial survival, not a vegetable planting calendar.
- databasedataset2026
USDA Natural Resources Conservation Service (2026). The PLANTS Database.
USDA NRCS · Accessed 2026-08-21 · Scope: USA and territories · Methods: Taxonomic database.
What it supports here. Accepted scientific names, synonyms, families and distribution used to normalise plant identity in this catalog. It does not describe companion relationships.
- journalfield1984
Uvah, I. I. I., Coaker, T. H. (1984). Effect of mixed cropping on some insect pests of carrots and onions.
Entomologia Experimentalis et Applicata · DOI 10.1111/j.1570-7458.1984.tb03422.x · Accessed 2026-08-21 · Scope: UK · Methods: Field trials of carrot–onion mixtures at different ratios.
What it supports here. Carrot fly damage fell only when onions greatly outnumbered carrots (roughly four onion rows per carrot row) and only before the onions started bulbing; at garden-typical ratios the effect was small or absent.
2 relationship records cite this source
