[{"id":"umn-companion","type":"extension","authors":"University of Minnesota Extension","title":"Companion planting in home gardens","publisher":"University of Minnesota Extension","year":2023,"url":"https://extension.umn.edu/gardening-minnesota/companion-planting-home-gardens","accessed":"2026-08-21","geographic_scope":"Minnesota, USA; general home-garden guidance","crops":["general","cabbage","tomato","onion","carrot","bean","corn","squash"],"methods":"Extension synthesis distinguishing research-backed examples from tradition.","evidence_context":"guidance","paraphrase":"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."},{"id":"umn-soil-rotation","type":"extension","authors":"University of Minnesota Extension","title":"Living soil, healthy garden: crop rotation and soil health","publisher":"University of Minnesota Extension","year":2023,"url":"https://extension.umn.edu/gardening-minnesota/living-soil-healthy-garden","accessed":"2026-08-21","geographic_scope":"Minnesota, USA; general","crops":["general"],"methods":"Extension synthesis.","evidence_context":"guidance","paraphrase":"Recommends rotating plant families between seasons to interrupt soil-borne disease and pest cycles, and explains how rotation differs from planting companions together."},{"id":"umn-diseases","type":"extension","authors":"University of Minnesota Extension","title":"Managing plant diseases in the home garden","publisher":"University of Minnesota Extension","year":2023,"url":"https://extension.umn.edu/planting-and-growing-guides/managing-plant-diseases-home-garden","accessed":"2026-08-21","geographic_scope":"USA; general","crops":["general","tomato","potato","cucurbits","brassicas"],"methods":"Extension synthesis.","evidence_context":"guidance","paraphrase":"Explains sanitation, rotation, spacing for airflow, resistant cultivars and watering practice as the core of home-garden disease management."},{"id":"sare-trap-crops","type":"government","authors":"Sustainable Agriculture Research and Education (SARE)","title":"Using trap crops to reduce pests (Crop Rotation on Organic Farms: Guidelines for intercropping)","publisher":"SARE / USDA","year":2009,"url":"https://www.sare.org/publications/crop-rotation-on-organic-farms/guidelines-for-intercropping/using-trap-crops-to-reduce-pests/","accessed":"2026-08-21","geographic_scope":"USA","crops":["squash","cucumber","cabbage","collards","mustard"],"methods":"Practitioner guidance synthesising research.","evidence_context":"guidance","paraphrase":"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."},{"id":"usda-plants","type":"database","authors":"USDA Natural Resources Conservation Service","title":"The PLANTS Database","publisher":"USDA NRCS","year":2026,"url":"https://plants.sc.egov.usda.gov/","accessed":"2026-08-21","geographic_scope":"USA and territories","crops":["general"],"methods":"Taxonomic database.","evidence_context":"dataset","paraphrase":"Accepted scientific names, synonyms, families and distribution used to normalise plant identity in this catalog. It does not describe companion relationships."},{"id":"kirsch-2023","type":"meta_analysis","authors":"Kirsch, F., et al.","title":"Intercropping, beneficial arthropods, and pests (meta-analysis; title as cited in the project research brief)","publisher":"Agriculture, Ecosystems & Environment","year":2023,"doi":"10.1016/j.agee.2023.108617","url":"https://doi.org/10.1016/j.agee.2023.108617","accessed":"2026-08-21","geographic_scope":"Global synthesis","crops":["general"],"methods":"Systematic review and meta-analysis of arthropod responses to intercropping.","evidence_context":"synthesis","paraphrase":"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.","notes":"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."},{"id":"carrillo-reche-2023","type":"meta_analysis","authors":"Carrillo-Reche, J., et al.","title":"Cabbage intercropping synthesis (meta-analysis; title as cited in the project research brief)","publisher":"Agriculture, Ecosystems & Environment","year":2023,"doi":"10.1016/j.agee.2023.108564","url":"https://doi.org/10.1016/j.agee.2023.108564","accessed":"2026-08-21","geographic_scope":"Global synthesis of cabbage intercropping trials","crops":["cabbage","clover","brassicas"],"methods":"Meta-analysis of field trials.","evidence_context":"synthesis","paraphrase":"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.","notes":"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."},{"id":"huss-2022","type":"journal","authors":"Huss, C. P., Holmes, K. D., Blubaugh, C. K.","title":"Benefits and risks of intercropping for crop resilience and pest management","publisher":"Journal of Economic Entomology","year":2022,"doi":"10.1093/jee/toac045","url":"https://doi.org/10.1093/jee/toac045","accessed":"2026-08-21","geographic_scope":"Global review","crops":["general"],"methods":"Narrative review of intercropping research.","evidence_context":"synthesis","paraphrase":"Intercropping can reduce pest pressure and increase resilience, but outcomes depend on the specific combination; costs include competition, labour and management complexity."},{"id":"bomford-2009","type":"journal","authors":"Bomford, M. K.","title":"Do tomatoes love basil but hate Brussels sprouts? Competition and land-use efficiency of popularly recommended and discouraged crop mixtures in biointensive agriculture systems","publisher":"Journal of Sustainable Agriculture","year":2009,"doi":"10.1080/10440040902835001","url":"https://doi.org/10.1080/10440040902835001","accessed":"2026-08-21","geographic_scope":"West Virginia, USA","crops":["tomato","basil","brussels-sprouts"],"methods":"Replicated field trials of crop mixtures at several densities; land equivalent ratio.","evidence_context":"field","paraphrase":"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."},{"id":"conboy-2019","type":"journal","authors":"Conboy, N. J. A., McDaniel, T., Ormerod, A., George, D., Gatehouse, A. M. R., Wharton, E., Donohoe, P., Curtis, R., Tosh, C. R.","title":"Companion planting with French marigolds protects tomato plants from glasshouse whiteflies through the emission of airborne limonene","publisher":"PLOS ONE","year":2019,"doi":"10.1371/journal.pone.0213071","url":"https://doi.org/10.1371/journal.pone.0213071","accessed":"2026-08-21","geographic_scope":"UK glasshouse","crops":["tomato","marigold"],"methods":"Glasshouse experiments with interplanted French marigolds and limonene dispensers.","evidence_context":"greenhouse","paraphrase":"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."},{"id":"hooks-2010","type":"journal","authors":"Hooks, C. R. R., Wang, K.-H., Ploeg, A., McSorley, R.","title":"Using marigold (Tagetes spp.) as a cover crop to protect crops from plant-parasitic nematodes","publisher":"Applied Soil Ecology","year":2010,"doi":"10.1016/j.apsoil.2010.09.005","url":"https://doi.org/10.1016/j.apsoil.2010.09.005","accessed":"2026-08-21","geographic_scope":"Review, mainly USA","crops":["marigold","tomato","general"],"methods":"Literature review of marigold cover-crop and intercrop trials.","evidence_context":"synthesis","paraphrase":"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."},{"id":"brennan-2016","type":"journal","authors":"Brennan, E. B.","title":"Agronomy of strip intercropping broccoli with alyssum for biological control of aphids","publisher":"Biological Control","year":2016,"doi":"10.1016/j.biocontrol.2016.02.015","url":"https://doi.org/10.1016/j.biocontrol.2016.02.015","accessed":"2026-08-21","geographic_scope":"Salinas Valley, California, USA (organic field production)","crops":["broccoli","sweet-alyssum","lettuce"],"methods":"Field trials of alyssum strips in organic broccoli.","evidence_context":"field","paraphrase":"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."},{"id":"hogg-2011","type":"journal","authors":"Hogg, B. N., Bugg, R. L., Daane, K. M.","title":"Attractiveness of common insectary and harvestable floral resources to beneficial insects","publisher":"Biological Control","year":2011,"doi":"10.1016/j.biocontrol.2010.09.007","url":"https://doi.org/10.1016/j.biocontrol.2010.09.007","accessed":"2026-08-21","geographic_scope":"California, USA","crops":["sweet-alyssum","coriander","dill","buckwheat","general"],"methods":"Field observation of beneficial insect visits to flowering plants.","evidence_context":"field","paraphrase":"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."},{"id":"finch-collier-2000","type":"journal","authors":"Finch, S., Collier, R. H.","title":"Host-plant selection by insects – a theory based on 'appropriate/inappropriate landings' by pest insects of cruciferous plants","publisher":"Entomologia Experimentalis et Applicata","year":2000,"doi":"10.1046/j.1570-7458.2000.00684.x","url":"https://doi.org/10.1046/j.1570-7458.2000.00684.x","accessed":"2026-08-21","geographic_scope":"UK","crops":["cabbage","brassicas","clover"],"methods":"Field and laboratory experiments on pest host-finding with background plants.","evidence_context":"field","paraphrase":"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."},{"id":"theunissen-1995","type":"journal","authors":"Theunissen, J., Booij, C. J. H., Lotz, L. A. P.","title":"Effects of intercropping white cabbage with clovers on pest infestation and yield","publisher":"Entomologia Experimentalis et Applicata","year":1995,"doi":"10.1111/j.1570-7458.1995.tb01868.x","url":"https://doi.org/10.1111/j.1570-7458.1995.tb01868.x","accessed":"2026-08-21","geographic_scope":"Netherlands","crops":["cabbage","clover"],"methods":"Field trials of cabbage undersown with clover.","evidence_context":"field","paraphrase":"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)."},{"id":"uvah-coaker-1984","type":"journal","authors":"Uvah, I. I. I., Coaker, T. H.","title":"Effect of mixed cropping on some insect pests of carrots and onions","publisher":"Entomologia Experimentalis et Applicata","year":1984,"doi":"10.1111/j.1570-7458.1984.tb03422.x","url":"https://doi.org/10.1111/j.1570-7458.1984.tb03422.x","accessed":"2026-08-21","geographic_scope":"UK","crops":["carrot","onion"],"methods":"Field trials of carrot–onion mixtures at different ratios.","evidence_context":"field","paraphrase":"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."},{"id":"cavanagh-2009","type":"journal","authors":"Cavanagh, A., Hazzard, R., Adler, L. S., Boucher, J.","title":"Using trap crops for control of Acalymma vittatum (Coleoptera: Chrysomelidae) reduces insecticide use in butternut squash","publisher":"Journal of Economic Entomology","year":2009,"doi":"10.1603/029.102.0319","url":"https://doi.org/10.1603/029.102.0319","accessed":"2026-08-21","geographic_scope":"Massachusetts and Connecticut, USA","crops":["winter-squash","cucumber","zucchini"],"methods":"On-farm trials of perimeter Blue Hubbard squash trap crops.","evidence_context":"field","paraphrase":"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."},{"id":"mitchell-2000","type":"journal","authors":"Mitchell, E. R., Hu, G., Johanowicz, D.","title":"Management of diamondback moth (Lepidoptera: Plutellidae) in cabbage using collard as a trap crop","publisher":"HortScience","year":2000,"doi":"10.21273/HORTSCI.35.5.875","url":"https://doi.org/10.21273/HORTSCI.35.5.875","accessed":"2026-08-21","geographic_scope":"Florida, USA","crops":["cabbage","collards"],"methods":"Field trials with collard perimeter rows around cabbage.","evidence_context":"field","paraphrase":"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."},{"id":"mt-pleasant-2016","type":"journal","authors":"Mt. Pleasant, J.","title":"Food yields and nutrient analyses of the Three Sisters: a Haudenosaunee cropping system","publisher":"Ethnobiology Letters","year":2016,"doi":"10.14237/ebl.7.1.2016.721","url":"https://doi.org/10.14237/ebl.7.1.2016.721","accessed":"2026-08-21","geographic_scope":"New York, USA","crops":["corn","pole-beans","winter-squash"],"methods":"Field plots comparing the Three Sisters polyculture with sole crops.","evidence_context":"field","paraphrase":"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."},{"id":"thilakarathna-2016","type":"journal","authors":"Thilakarathna, M. S., McElroy, M. S., Chapagain, T., Papadopoulos, Y. A., Raizada, M. N.","title":"Belowground nitrogen transfer from legumes to non-legumes under managed herbaceous cropping systems. A review","publisher":"Agronomy for Sustainable Development","year":2016,"doi":"10.1007/s13593-016-0396-4","url":"https://doi.org/10.1007/s13593-016-0396-4","accessed":"2026-08-21","geographic_scope":"Global review","crops":["beans","peas","clover","general"],"methods":"Literature review of nitrogen transfer studies.","evidence_context":"synthesis","paraphrase":"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."},{"id":"letourneau-2011","type":"meta_analysis","authors":"Letourneau, D. K., et al.","title":"Does plant diversity benefit agroecosystems? A synthetic review","publisher":"Ecological Applications","year":2011,"doi":"10.1890/09-2026.1","url":"https://doi.org/10.1890/09-2026.1","accessed":"2026-08-21","geographic_scope":"Global synthesis","crops":["general"],"methods":"Meta-analysis of 552 experiments.","evidence_context":"synthesis","paraphrase":"Diversified cropping systems generally reduced herbivore pests and increased natural enemies compared with monocultures, with crop damage lower on average; yield responses were mixed."},{"id":"shelton-2006","type":"journal","authors":"Shelton, A. M., Badenes-Perez, F. R.","title":"Concepts and applications of trap cropping in pest management","publisher":"Annual Review of Entomology","year":2006,"doi":"10.1146/annurev.ento.51.110104.150959","url":"https://doi.org/10.1146/annurev.ento.51.110104.150959","accessed":"2026-08-21","geographic_scope":"Global review","crops":["general","cabbage","squash"],"methods":"Review of trap cropping theory and cases.","evidence_context":"synthesis","paraphrase":"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."},{"id":"cook-2007","type":"journal","authors":"Cook, S. M., Khan, Z. R., Pickett, J. A.","title":"The use of push-pull strategies in integrated pest management","publisher":"Annual Review of Entomology","year":2007,"doi":"10.1146/annurev.ento.52.110405.091407","url":"https://doi.org/10.1146/annurev.ento.52.110405.091407","accessed":"2026-08-21","geographic_scope":"Global review","crops":["corn","general"],"methods":"Review.","evidence_context":"synthesis","paraphrase":"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."},{"id":"brooker-2015","type":"journal","authors":"Brooker, R. W., et al.","title":"Improving intercropping: a synthesis of research in agronomy, plant physiology and ecology","publisher":"New Phytologist","year":2015,"doi":"10.1111/nph.13132","url":"https://doi.org/10.1111/nph.13132","accessed":"2026-08-21","geographic_scope":"Global synthesis","crops":["general"],"methods":"Review.","evidence_context":"synthesis","paraphrase":"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."},{"id":"duke-2015","type":"journal","authors":"Duke, S. O.","title":"Proving allelopathy in crop–weed interactions","publisher":"Weed Science","year":2015,"doi":"10.1614/WS-D-13-00130.1","url":"https://doi.org/10.1614/WS-D-13-00130.1","accessed":"2026-08-21","geographic_scope":"Global review","crops":["general"],"methods":"Review of allelopathy methodology.","evidence_context":"synthesis","paraphrase":"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."},{"id":"osu-growing-your-own","type":"extension","authors":"Oregon State University Extension Service","title":"Growing Your Own (EM 9027)","publisher":"Oregon State University Extension","year":2019,"url":"https://extension.oregonstate.edu/catalog/pub/em-9027-growing-your-own","accessed":"2026-08-21","geographic_scope":"Oregon, USA (Pacific Northwest)","crops":["general"],"methods":"Extension growing guide with planting dates, spacing and culture.","evidence_context":"guidance","paraphrase":"Region-specific planting dates, spacing and cultural requirements for common vegetables in western and eastern Oregon, used here for Pacific Northwest calendar assumptions."},{"id":"cornell-growing-guides","type":"extension","authors":"Cornell University, Cornell Cooperative Extension","title":"Vegetable Growing Guides (Cornell Garden-Based Learning)","publisher":"Cornell University","year":2024,"url":"https://gardening.cals.cornell.edu/vegetable-growing-guides/","accessed":"2026-08-21","geographic_scope":"New York, USA; temperate general","crops":["general"],"methods":"Extension growing guides.","evidence_context":"guidance","paraphrase":"Crop-by-crop guidance on sowing, transplanting, spacing, days to maturity, water and common problems used for catalog culture fields."},{"id":"rhs-grow-your-own","type":"extension","authors":"Royal Horticultural Society","title":"Grow Your Own vegetables, herbs and fruit","publisher":"Royal Horticultural Society","year":2025,"url":"https://www.rhs.org.uk/vegetables","accessed":"2026-08-21","geographic_scope":"United Kingdom; temperate maritime","crops":["general"],"methods":"Horticultural society growing guides.","evidence_context":"guidance","paraphrase":"Cultivation guidance for cool-temperate maritime climates, including sowing months, spacing, support and container suitability."},{"id":"uc-ipm-home","type":"extension","authors":"University of California Statewide Integrated Pest Management Program","title":"Home, garden, turf and landscape pests","publisher":"UC Agriculture and Natural Resources","year":2025,"url":"https://ipm.ucanr.edu/home-and-landscape/","accessed":"2026-08-21","geographic_scope":"California, USA; pest biology broadly applicable","crops":["tomato","corn","cucurbits","brassicas","general"],"methods":"IPM pest notes.","evidence_context":"guidance","paraphrase":"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."},{"id":"usda-hardiness","type":"government","authors":"USDA Agricultural Research Service","title":"USDA Plant Hardiness Zone Map","publisher":"USDA ARS","year":2023,"url":"https://planthardiness.ars.usda.gov/","accessed":"2026-08-21","geographic_scope":"USA","crops":["general"],"methods":"Climate mapping from average annual minimum temperature.","evidence_context":"dataset","paraphrase":"Zones describe average winter minimum temperature only; they are an input for perennial survival, not a vegetable planting calendar."},{"id":"noaa-normals","type":"government","authors":"NOAA National Centers for Environmental Information","title":"U.S. Climate Normals (1991–2020)","publisher":"NOAA NCEI","year":2021,"url":"https://www.ncei.noaa.gov/products/land-based-station/us-climate-normals","accessed":"2026-08-21","geographic_scope":"USA","crops":["general"],"methods":"Station climate normals including frost probabilities.","evidence_context":"dataset","paraphrase":"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."},{"id":"brennan-2013","type":"journal","authors":"Brennan, E. B.","title":"Agronomic aspects of strip intercropping lettuce with alyssum for biological control of aphids","publisher":"Biological Control","year":2013,"doi":"10.1016/j.biocontrol.2013.03.017","url":"https://doi.org/10.1016/j.biocontrol.2013.03.017","accessed":"2026-08-21","geographic_scope":"Salinas Valley, California, USA (organic field production)","crops":["lettuce","sweet-alyssum"],"methods":"Field trials of alyssum interplanted in organic romaine lettuce at several ratios.","evidence_context":"field","paraphrase":"Replacing a small share of lettuce plants with alyssum supported hoverflies for aphid control; low alyssum ratios limited the loss of lettuce yield."},{"id":"hokkanen-1991","type":"journal","authors":"Hokkanen, H. M. T.","title":"Trap cropping in pest management","publisher":"Annual Review of Entomology","year":1991,"doi":"10.1146/annurev.en.36.010191.001003","url":"https://doi.org/10.1146/annurev.en.36.010191.001003","accessed":"2026-08-21","geographic_scope":"Global review","crops":["general"],"methods":"Review.","evidence_context":"synthesis","paraphrase":"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."}]