Garlic Companion Planting
Allium sativum
Allium (Amaryllidaceae) -- cool season
Good Companions for Garlic
Garlic volatiles (allyl sulfides) deter aphids and flea beetles on adjacent brassicas. Garlic extracts also show antifungal activity against Sclerotinia sclerotiorum and Botrytis cinerea.
Fall-plant garlic in beds that will receive spring brassica transplants.
- Volatile compounds from Allium spp. affecting insect behavior -- Phytochemistry (2004)
- Garlic as a companion crop for pest management in brassicas -- UMass Extension Vegetable Program (2019)
Garlic allyl sulfide volatiles deter flea beetles (Phyllotreta spp.) and aphids that commonly attack bok choy. Garlic also shows antifungal activity against soil-borne pathogens.
Fall-planted garlic provides established volatile emission when spring bok choy is transplanted.
- Volatile compounds from Allium spp. affecting insect behavior -- Phytochemistry (2004)
Garlic allyl sulfide volatiles provide olfactory masking that reduces carrot fly oviposition. Garlic also shows antifungal activity against Alternaria dauci (carrot leaf blight) in laboratory assays.
Fall-planted garlic overwinters well next to spring-sown carrots.
- Effect of Allium spp. volatiles on the behaviour of Psila rosae -- IOBC/WPRS Bulletin (1997)
- Antifungal activity of garlic extracts against plant pathogenic fungi -- Phytoparasitica (2008)
Garlic volatiles (allyl disulfides, diallyl trisulfide) deter spider mites (Tetranychus urticae) and show antifungal activity against Botrytis cinerea (gray mold) and Colletotrichum acutatum (anthracnose), two major strawberry pathogens.
Fall-planted garlic overwinters well alongside strawberry beds. Interplant within the strawberry rows for closest proximity.
- Antifungal activity of garlic extracts against strawberry pathogens -- Crop Protection (2009)
- Spider mite management using allyl isothiocyanate and related compounds -- Journal of Economic Entomology (2011)
- Intercropping garlic in strawberry fields for pest management -- HortScience (2015)
Garlic allyl sulfide compounds deter lettuce aphids (Nasonovia ribisnigri). Fall-planted garlic provides early-season volatile emission when spring lettuce is most vulnerable to aphid colonization.
Garlic planted in fall is already established when spring lettuce goes in. Efficient use of bed space.
- Garlic intercropping effects on pest suppression in lettuce -- Journal of Sustainable Agriculture (2010)
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)
Garlic allyl sulfide compounds deter leaf miners (Liriomyza spp.) and aphids that commonly attack Swiss chard. Garlic antifungal properties may reduce Cercospora leaf spot pressure.
Interplant garlic among chard or use garlic as a border planting.
- Antifungal activity of garlic extracts against plant pathogenic fungi -- Phytoparasitica (2008)
Garlic volatiles deter aphids and other sap-sucking insects from rhubarb. Both are perennial/semi-perennial crops that can coexist long-term. Garlic antifungal properties may reduce crown rot.
Plant garlic around the perimeter of rhubarb crowns. Both are cold-hardy perennials.
- Volatile compounds from Allium spp. affecting insect behavior -- Phytochemistry (2004)
Garlic volatiles deter aphids and leaf miners on radicchio. Garlic antifungal compounds may reduce Sclerotinia and Botrytis risk on radicchio heads.
Interplant garlic among fall radicchio plantings.
- Antifungal activity of garlic extracts against plant pathogenic fungi -- Phytoparasitica (2008)
Garlic volatiles deter Japanese beetle (Popillia japonica) and spider mites that damage raspberry canes and foliage. Garlic antifungal properties may reduce anthracnose and other cane diseases.
Plant garlic along raspberry rows. Fall-planted garlic establishes before spring growth begins.
- Antifungal activity of garlic extracts against plant pathogenic fungi -- Phytoparasitica (2008)
- Japanese beetle management in small fruits -- Penn State Extension (2019)
Crops to Avoid Near Garlic
Garlic root exudates contain allyl disulfides and other organosulfur compounds that suppress Rhizobium populations, reducing biological nitrogen fixation in adjacent legumes.
Same allium-legume antagonism. Keep garlic beds well separated from all bean and pea plantings.
- Allelopathic effects of Allium species on legume Rhizobium symbiosis -- Plant and Soil (1996)
Garlic organosulfur compounds inhibit Rhizobium bacteria that form nitrogen-fixing nodules on pea roots, reducing the primary agronomic benefit of pea cultivation.
Applies to all pea types (snap, shelling, snow) and all alliums.
- Allelopathic effects of Allium species on legume Rhizobium symbiosis -- Plant and Soil (1996)
Garlic organosulfur compounds inhibit Rhizobium bacteria that form nitrogen-fixing nodules on pea roots. Same allium-legume antagonism.
Applies to all pea types and all alliums.
- Allelopathic effects of Allium species on legume Rhizobium symbiosis -- Plant and Soil (1996)
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