Do not plant lettuce or its family in ground that held it within 3 years
Do not plant lettuce or its family in ground that held it within 3 years, and know that lettuce drop's fungi live on most other vegetables too.
A good hunch A person has checked it against its sources. If you skip this, you lose real yield. The planner suggests it.
How it works
Bottom rot (Rhizoctonia solani) and lettuce drop (Sclerotinia sclerotiorum and S. minor) survive in soil as mycelium and sclerotia for years and build where lettuce repeats; a three-year break holds bottom rot down. Drop's fungi infect alliums, brassicas, nightshades, cucurbits and legumes as well, so a lettuce rotation slows them without starving them, and only cereals are safe ground.
What to do about it
Plant lettuce and its family in different ground, or wait until 3 years have passed since this ground last held them. Where drop has shown, the break that counts is one of grains or corn, since most vegetables carry it, and dead plants go in the bin. Keep them out of the compost, because the sclerotia survive it.
How much it matters: Cornell's rotation table: lettuce bottom rot 3 years, drop 3 years. NC State: the broad host range 'significantly limits the efficacy of crop rotation'; cereals are less susceptible. USU: rotate with non-susceptible crops such as grains or corn. UMass: sclerotia survive in the soil for many years.
The evidence
Evidence: checked against 4 sources in the research-based literature.
The 4 sources
Bottom rot (Rhizoctonia) | 3 years
Sclerotinia sclerotiorum and S. minor have a wide host range infecting allium (onion, garlic), brassica (cabbage, broccoli), solanaceae (pepper, potato), cucurbits (cucumber, squash), lettuce, and sweetpotato crops
The sclerotia can survive dormant in the soil for extended periods
Rhizoctonia survives in the soil, as mycelium or sclerotia
Plants it applies to · 13
Flowers · 7, Salad & greens · 3, Herbs · 2, Perennial vegetables · 1
Herbs · 2
Perennial vegetables · 1
How this rule has changed
Every change is dated, newest first. The full record, with each reason, is in the data download.
- Sources updated
- Wording made clearer
- Added to the rules
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Cite this page
Milpa Gardens. “Do not plant lettuce or its family in ground that held it within 3 years, and know that lettuce drop's fungi live on most other vegetables too.” Evidence grade: A good hunch. https://milpa.garden/rules/do-not-plant-lettuce-family-ground-that/
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