Companion planting

Friendly neighbors and a few combinations to give extra space. Pairs with What can I grow? when you are sketching beds. For fallow gaps and soil recovery, see cover crops.

Type

All Good neighbors Give space

Crop focus

Any Tomato Pepper / eggplant Brassicas Squash / cucumber Beans / peas Carrot / root crops Corn Lettuce / greens Radish Onion / garlic Herbs

Benefit

Any Pest confusion / trap Pollinators Shade or shelter Soil / roots Kitchen / flavor

Carrot & onion familyPair
Carrots · Onions or leeks
Onion scent can help mask carrot rows from carrot rust fly in backyard scales; different root depths reduce direct competition.
Pole beans & corn (three sisters lite)Pair
Sweet corn · Pole beans
Beans can climb corn after corn is knee-high; beans fix little N for the same-year corn crop, but roots loosen soil around the stalk.
Cucumber & radishPair
Cucumbers · Radishes
Radishes mark rows and mature fast while cucumbers warm up; radishes can flag soil crusting issues early.
Lettuce under tomatoes (spring)Pair
Lettuce / arugula · Tomatoes (young)
Early lettuce enjoys light shade from small tomato plants; remove or harvest lettuce before the tomato canopy closes and holds moisture on leaves overnight.
Peppers & spinach (shoulder season)Pair
Peppers · Spinach
Spinach enjoys afternoon shade from pepper bushes in hot summers; pull spinach before it bolts into pepper fruiting season crowding.
Avoid: tomato & fennelAvoid
Tomatoes · Fennel
Fennel can allelopathically stress some neighbors; tomatoes near vigorous fennel often look unhappy. Keep fennel in its own corner or container.
Avoid: tight tomato + brassica spacingAvoid
Tomatoes · Broccoli / kale
Both are heavy feeders with big root systems; crammed together they compete for water and nutrients and reduce airflow.
Avoid: fresh allium row next to beans/peasAvoid
Onions / garlic (active row) · Beans or peas
Folk guidance plus some field experience: very close alliums can slow legumes for unclear reasons—separate rows or time succession so peaks do not overlap.
Avoid: vegetables under black walnutAvoid
Nightshades / cucurbits (many) · Black walnut canopy / roots
Juglone from walnut roots and litter harms many vegetables. Map walnut driplines and keep food beds outside that zone or use raised beds with barriers—research your species.