Tomato Companion Planting
Solanum lycopersicum
Nightshade (Solanaceae) -- warm season
Good Companions for Tomato
Basil volatiles (linalool, 1,8-cineole) reduce whitefly (Bemisia tabaci) oviposition on neighboring tomato plants. Field trials show 20-40% reduction in whitefly populations when basil is interplanted with tomato.
Interplant basil every 3-4 tomato plants. Allow some basil to flower for maximum volatile emission.
- Companion planting -- do aromatic plants disrupt host-plant finding by the tomato whitefly (Bemisia tabaci) in a tomato crop? -- International Journal of Pest Management (2010)
- Aromatic Plants as a Tool in Pest Management -- University of Florida IFAS Extension (2018)
Intercropping tomatoes with carrots uses vertical space efficiently -- tomato canopy shades cool-season carrots, extending harvest. Tomato root exudates have shown some deterrent effect on carrot fly (Psila rosae) in choice assays.
Plant carrots between tomato rows. Carrots benefit more from the pairing than tomatoes.
- Intercropping of tomato and carrot: effects on pest incidence and yield -- Acta Horticulturae (2004)
Nasturtium functions as a trap crop for aphids (Myzus persicae, Aphis gossypii), concentrating colonies away from tomato. Nasturtium also attracts predatory hover flies (Syrphidae) that consume aphids.
Plant nasturtiums as a border around tomato beds. Inspect nasturtiums regularly for heavy aphid buildup.
- Trap Crops for Managing Insect Pests -- University of Connecticut Extension (2012)
- The role of trap cropping in vegetable pest management -- Integrated Pest Management Reviews (1998)
Borage (Borago officinalis) flowers are highly attractive to pollinating bees and parasitoid wasps. Interplanting with tomato increases pollinator visitation rates, potentially improving fruit set.
Borage self-seeds readily. Plant at bed edges to avoid crowding tomatoes.
- Insect Visitors to Flowering Herbs and Their Potential Contribution to Biocontrol -- Environmental Entomology (2003)
Sweet alyssum (Lobularia maritima) flowers attract hover flies (Syrphidae) whose larvae are voracious aphid predators. Living mulch of alyssum between tomato rows also suppresses weeds and conserves soil moisture.
Sow alyssum between tomato rows or at bed edges. Reseeds freely once established.
- Insectary plantings: practical applications for biological control -- California Agriculture (UC ANR) (2006)
- Flower power: promoting pest natural enemies with sweet alyssum -- HortScience (2013)
Flowering parsley attracts Trichogramma wasps and hover flies (Syrphidae) that parasitize or prey on tomato hornworm (Manduca quinquemaculata) and other Lepidopteran pests.
Allow second-year parsley to flower. Provides ground cover and moisture conservation around tomato base.
- The role of Apiaceae floral resources in supporting beneficial insects -- Journal of Insect Conservation (2006)
- Companion plants for natural pest management -- Penn State Extension (2019)
Garlic root exudates and decomposing residues release allicin and related organosulfur compounds that suppress soil-borne fungi including Fusarium oxysporum and Verticillium dahliae.
Interplant garlic among tomatoes or use garlic residue as mulch. Particularly valuable in disease-prone soils.
- Antifungal activity of garlic extracts against plant pathogenic fungi -- Phytoparasitica (2008)
- Soil amendment with allium species for suppression of soil-borne diseases -- Plant Pathology (2010)
Calendula attracts hover flies (Syrphidae) and parasitoid wasps. Sticky trichomes on calendula foliage physically trap whiteflies (Trialeurodes vaporariorum). Interplanting reduces overall pest load on tomato.
Interplant calendula throughout tomato beds. Calendula also tolerates cooler temperatures, extending its usefulness.
- Biological control of glasshouse whitefly using insectary plants -- IOBC/WPRS Bulletin (2003)
- Companion planting with flowering plants for pest management -- Journal of Sustainable Agriculture (2010)
Phacelia (Phacelia tanacetifolia) is one of the most effective insectary plants for attracting hover flies, parasitoid wasps, and predatory beetles. Each phacelia plant can support production of thousands of hover fly larvae that consume aphids.
Sow phacelia at tomato bed borders. Also excellent as a cover crop that attracts beneficials when it blooms before incorporation.
- Phacelia tanacetifolia as an insectary plant for conservation biological control -- BioControl (2007)
- Insectary plantings: practical applications for biological control -- California Agriculture (UC ANR) (2006)
French marigold (Tagetes patula) root exudates contain alpha-terthienyl, a nematicide that suppresses root-knot nematodes (Meloidogyne spp.). This effect requires marigolds to be grown for a full season in the same soil.
French marigolds (Tagetes patula) are more effective than African marigolds (T. erecta) for nematode suppression. Grow for a full season before planting tomatoes in the same bed.
- Suppressive effect of Tagetes spp. on Meloidogyne species -- Nematropica (2000)
- Managing nematodes with marigolds -- UC IPM Pest Management Guidelines (2018)
- Marigolds (Tagetes spp.) for nematode management -- University of Florida IFAS Extension (2019)
Hairy vetch (Vicia villosa) cover crop fixes 100-200 lb N/acre and suppresses weeds when used as rolled/crimped mulch for no-till tomato production. Tomato yields in vetch mulch systems match or exceed conventional management.
Plant hairy vetch in fall, roll/crimp at flowering in spring, transplant tomatoes into the mulch. Outstanding weed suppression.
- Hairy vetch mulch for organic no-till tomato production -- HortScience (2008)
- Managing cover crops profitably -- USDA SARE (2012)
Tomato plants contain solanine and tomatine glycoalkaloids that deter asparagus beetle (Crioceris asparagi). Asparagus root exudates may suppress root-knot nematodes (Meloidogyne spp.) that affect tomato.
Plant tomatoes adjacent to asparagus bed edges, not within the perennial bed itself.
- Asparagus beetle management through companion planting -- Cornell Cooperative Extension (2017)
- Nematicidal potential of asparagic acid from Asparagus -- Journal of Agricultural and Food Chemistry (2006)
Lemon balm (Melissa officinalis) volatiles (citral, geraniol) attract pollinators and deter whiteflies. Lemon balm flowers are highly attractive to bees and parasitoid wasps.
Lemon balm spreads by seed and rhizome. Contain in a dedicated area or pot near tomatoes.
- Aromatic Plants as a Tool in Pest Management -- University of Florida IFAS Extension (2018)
Lovage (Levisticum officinale) flowers, like other Apiaceae, attract parasitoid wasps (Trichogramma, Cotesia spp.) and predatory hover flies that control tomato pests.
Lovage grows very tall (1-2 meters). Plant at the north end of beds to avoid shading tomatoes.
- The role of Apiaceae floral resources in supporting beneficial insects -- Journal of Insect Conservation (2006)
Coneflower (Echinacea purpurea) attracts a wide range of predatory insects including parasitoid wasps, ladybugs, and lacewings. As a perennial, it provides stable beneficial insect habitat season after season.
Plant coneflower as a permanent border near annual vegetable beds. Flowers from midsummer through fall.
- Native perennial plants as insectary resources in agricultural landscapes -- Environmental Entomology (2008)
Crops to Avoid Near Tomato
Fennel (Foeniculum vulgare) root exudates contain trans-anethole and other volatile compounds with demonstrated allelopathic effects. These compounds inhibit seed germination and seedling growth of many vegetable crops including tomato.
Grow fennel isolated from all vegetable beds. Best in its own container or a separate garden section.
- Allelopathic potential of fennel (Foeniculum vulgare Mill.) -- Allelopathy Journal (2007)
- Allelopathic effect of some medicinal plants on seed germination -- Journal of Agronomy (2005)
Both are Solanaceae and share susceptibility to Phytophthora infestans (late blight), Alternaria solani (early blight), and Verticillium dahliae (verticillium wilt). Growing in proximity increases inoculum pressure for all three pathogens.
Separate tomato and potato in the garden. Also separate in crop rotation -- do not follow one with the other.
- Epidemiology of late blight (Phytophthora infestans) in tomato and potato -- Annual Review of Phytopathology (2009)
- Managing Late Blight in Tomato and Potato -- Cornell Cooperative Extension (2019)