What to plant next to Romaine lettuce

The neighbours on this page are sorted by what the evidence shows: a proven benefit, good with a condition, simply compatible, or to keep apart. Each group says why, and the sources are listed at the end of the page.

Proven benefit

Sweet alyssum

Sweet alyssum flowers draw hoverflies, whose larvae eat the aphids on lettuce. A few plants among the lettuces are enough (research in organic lettuce fields in California).

Compatible

They grow together without a known conflict, but the benefits traditionally claimed for these pairings are not proven.

Why it helps

Mixing crops in the same bed spreads the risk: pests find their target harder, the soil is used at different depths and flowers bring in the insects that pollinate and hunt aphids.

Spacing in the row	25 cm (10 in)
In a 30 cm (1 ft) square	4 per square
Crop rotation group	Anywhere in the rotation
Sow outdoors	Mar–Aug
Harvest	May–Oct

Romaine lettuce: spacing, plants per square and companions →

Plan it in the garden

The planner warns you when two crops with a documented shared risk, such as tomatoes and potatoes, end up next to each other, so you can fix the layout before planting.

Start Planning Your Garden

Sources

The class of each neighbour on this page rests on these sources.

Del-Pozo Valdivia confirms the benefit of insectary plants in lettuce (2019) — UC Statewide IPM Program for: proven benefit, compatible; checked 2026-10-31
The Myth of Companion Plantings (L. Chalker-Scott) — Washington State University Extension for: compatible; checked 2026-10-28
Efficient intercropping for biological control of aphids in transplanted organic lettuce (E. Brennan) — USDA Agricultural Research Service, via eOrganic for: proven benefit; checked 2026-10-31
Insectary crops to enhance syrphid fly activity in organic lettuce on California’s Central Coast — Entomological Society of America, 2006 meeting (UC Cooperative Extension) for: compatible; checked 2026-10-31