Common NameScientific NameHelpsHelped byAttractsRepelsAvoidComments
GeraniumsPelargoniumspp.Roses, corn, peppers, grapesleafhoppers, Japanese beetlesTomatoes, Tobacco, Eggplants and other nightshadesA trap crop, attracting pests away from roses and grape vines, distracts beet leafhoppers, carrier of the curly top virus, keep away from Solanaceous plants like eggplant, and tobacco
LupinLupinusCucurbits, brassica, lettuce, rosemary, dill, strawberrysummer savoryHoneybeestomatoes and other solanaceaeThis wildflower is a legume, hosting bacteria that fixes nitrogen in the soil, fertilizing it for neighboring plants
MarigoldAsteraceae Calendula Tagetesmost plants, especially tomatoes and peppers, cucurbits (cucumbers, gourds, squash), brassicas (broccoli, kale, cabbage)snailsnematodes, beet leaf hoppers, other pestsMarigolds are a wonder-drug of the companion plant world, invoking the saying "plant them everywhere in your garden". French marigolds produce a pesticidal chemical from their roots, so strong it lasts years after they are gone. Mexican marigolds do the same, but are so strong they will inhibit the growth of some more tender herbs. Certain Varieties of marigolds (Tagetes) can help manage eelworms (Root-knot nematode) when planted the year before [1].
Tagetes has also been found effective against perennial weeds such as Ranunculus ficaria (Celandine), Aegopodium podagraria (Ground elder), Glechoma hederacea (Ground ivy), Agropyron repens (Couch grass), Convolvulus arvensis (Field bindweed), Equisetum arvense (Field/Common Horsetail) and other 'starchy' weeds.[citation needed]
PetuniaPetunia x hybridacucurbits (squash, pumpkins, cucumbers), asparagusleafhoppers, Japanese beetles, aphids, asparagus beetleIs a trap crop almost identical to geraniums in function
NasturtiumTropaeolum majusMany plants, especially cucurbits (melons, cucumbers, gourds), beans, tomatoes, apple trees, brassicas (broccoli, cabbage, etc.), radishpredatory insectsaphids, cabbage looper, squash bug, white fly, cucumber beetlesradish, cauliflowerBoth work as trap crops for aphids, is among the best at attracting predatory insects[citation needed]
SunflowerHelianthus annuuscorn, tomatoesaphidsWas grown as a companion for corn(maize) before modern Europeans arrived in the Americas, supposedly increases their production, ants herd aphids onto sunflowers, keeping them off neighboring plants
TansyTanacetum vulgarecucurbits (cucumbers, squash, etc.), raspberries and relatives, roses, cornsugar ants, Japanese beetles, cucumber beetles, squash bugs, miceToxic to many animals, don't plant it where livestock browse
YarrowAchillea millefoliummany plantspredatory wasps, ladybugs, hoverflies, damselbugsMay increase the essential oil production of some herbs. Also improves soil quality, use the leaves to enrich compost, or as mulch.
ZinniaZinniabeans, tomatoes, pepperswhitefliesAttracts hummingbirds that eat whitflies, attracts pollinators