Don't plant nightshades where nightshades grew in the last 3 years
As recorded: Do not plant Solanaceae in ground that held Solanaceae within 3 years.
Promising A person has checked it against its sources. If you skip this, you lose real yield. The planner warns you.
How it works
Alternaria solani (early blight) and Septoria lycopersici overwinter on tomato debris and solanaceous weeds; a 2-3 year break plus debris removal starves this inoculum. Fusarium has a very narrow host range, so rotating away from the host is effective. Verticillium is the exception. Its microsclerotia persist ~10 years and it infects 300+ host families, so a garden-scale rotation does not control it.
What to do about it
Plant nightshades in different ground, or wait until 3 years have passed since this ground last held them. Clear and remove the old debris either way, because the inoculum overwinters on it.
How much it matters: 3-year nightshades interval is the standard extension recommendation and targets the debris-borne diseases (early blight, Septoria). It does not control Verticillium, whose microsclerotia persist ~10 years across an extremely broad host range.
The evidence
Evidence: checked against 5 sources in the research-based literature.
The 5 sources
… tomatoes and related vegetables, such as potatoes, peppers, and eggplants, should not be planted on the same land more than once in three years.
The fungus is known to overwinter on infected tomato debris and solanaceous weed hosts
The pathogen can survive in the soil without a host for up to 10 years in the form of structures called microsclerotia
Verticillium wilt tends to affect a wide range of hosts and can infect many unrelated plants. Fusarium spp., on the other hand, have very narrow host ranges.
Plants it applies to · 5
Fruiting vegetables · 4, Roots & tubers · 1
Roots & tubers · 1
Folklore it answers
Read next
- Do you need to rotate crops in a raised bed?Yes. The pests and diseases live in the soil, so a raised bed needs rotating like any ground. Here's why, and why digging out the soil is the costly way to do the same job.
- Crop rotation for the home gardenMove crops by plant family so soil-borne pests and diseases can't settle in. What to rotate, how far apart, and what rotation can and can't do.
- Don't plant berries where the tomatoes were: the rotation rule that rotation missesYou can rotate perfectly, wait three years, clear the debris, and still kill a raspberry patch. Verticillium ignores plant families and lingers in soil for years.
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
- Wording made clearer
- Advice on what to do added
- A person read the sources and confirmed it
- Sources updated
- Added to the rules
You must rotate every crop to new ground every single year. · What can I plant now?
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Cite this page
Milpa Gardens. “Don't plant nightshades where nightshades grew in the last 3 years.” Evidence grade: Promising. https://milpa.garden/rules/do-not-plant-nightshades-ground-that-held/
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- Well established
- The rule names its mechanism and is settled, by sources a person has read and checked or by plain arithmetic and geometry.
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- The mechanism is named and the literature backs it. A few questions are still open.
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- Plausible by its mechanism, but field studies are thin, so treat it as a lean.
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- The evidence points both ways, or no study has tested it, so the planner does not enforce it.
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