Can you plant onions and lettuce together?

Charts say yes. Nobody has tested onions with lettuce, as far as we could find.

Why we can't give a firm answer

Garden charts recommend it. 4 garden chart entries recommend growing them together. 3 of them cite no source. Charts pass on gardening tradition; they are not tests.
Companion planting: A method for sustainable pest control (Riesselman · Iowa State University)

What to plant with onions and lettuce

Good neighbours of both, best tested first.

BeetWith onions: 64% more harvestWith lettuce: 58% more harvest
CucumberWith onions: Helpful plant chemistryWith lettuce: 35% more harvest
DillWith onions: Draws in pest-eating insectsWith lettuce: Recommended by garden charts, not tested
KohlrabiRecommended by garden charts for both, not tested yet

How each one was tested, with the evidence

What to keep away from onions and lettuce

PeaWith onions: Garden charts advise against it, not tested
AsparagusWith onions: Garden charts advise against it, not tested
CeleryWith lettuce: Garden charts advise against it, not tested
ParsleyWith lettuce: Garden charts advise against it, not tested

The evidence in detail

For readers who want to dig in: every chart entry, study and yield trial behind the answer above, with the numbers.

Tradition, research and yield trials

Tradition

Good

avoidgood

4 chart entries: 4 recommend, 0 advise against.

1 cited, 3 uncited.

Research

No papers found on this pair.

Yield trial

No intercropping yield trial.

Untested folklore

Companion plants for both onions and lettuce

Plants that are good neighbours of each. Biggest harvest gain first; each cell links to the evidence for that pair.

Plant	With onions	With lettuce
Beet	64% more harvest from the same spaceField trial, 1 study. Charts: recommend.Evidence for onions and beets	58% more harvest from the same spaceField trial, 1 study. Charts: recommend.Evidence for lettuce and beets
Cucumber	Helpful plant chemistry and bigger combined harvestField trial, 3 studies. Charts: recommend.Evidence for onions and cucumbers	Fewer pests35% more harvest from the same spaceField trial, 5 studies. Charts: recommend.Evidence for lettuce and cucumbers
Dill	Draws in pest-eating insectsField trial, 1 study. Charts: recommend.Evidence for onions and dill	No trial foundNot tested. Charts: recommend.Evidence for lettuce and dill

Harvest from the same space compares a bed with both crops against the same area split into single-crop beds, counting the harvest of both crops (the land equivalent ratio in yield trials).

Recommended by garden charts for both, not tested yet

Kohlrabi

The evidence, with sources

TraditionGood4 entries

GoodLettuce helps Onion
Lettuce: helps onions
List of companion plants (uncited entry) (Wikipedia)
GoodOnion helps Lettuce
Lettuce: helped by onions
Companion planting: A method for sustainable pest control (Riesselman · Iowa State University)
GoodOnion helps Lettuce
Onion: helps lettuce
List of companion plants (uncited entry) (Wikipedia)
GoodLettuce helps Onion
Onion: helped by lettuce
List of companion plants (uncited entry) (Wikipedia)

Plan a bed with onions and lettuce

All neighbours of onion and of lettuce, or every pair at once in the companion planting chart.

Have you grown onions and lettuce together?

Tell other gardeners what happened: spacing, pests, harvest, or ask a question. Reader notes are not checked by us and do not change the verdicts on this page.