Do not plant beets, chard, spinach or amaranth in ground that held them 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
Cercospora beticola, the leaf spot of beet, chard and spinach, survives on infested residue and in soil for up to three years and carries over on lambsquarters and pigweed; spinach downy mildew (Peronospora effusa) leaves oospores in the soil for a few years and rides on seed. A three-year break outlasts both.
What to do about it
Plant them in different ground, or wait until 3 years have passed since this ground last held them. Bury or remove the old leaves, keep lambsquarters and pigweed out of the bed in between, and buy clean seed.
How much it matters: Cornell: at least 3 years for Cercospora on table beet, and 2-3 years out of spinach for downy mildew; Penn State and UMD: 3 years; UMass: 2-3 years, the fungus surviving up to two years in soil; Cornell's rotation table: beet 3, spinach 2.
The evidence
Evidence: checked against 7 sources in the research-based literature.
The 7 sources
Rotate with non-host crops for at least 3 years
Beet growers wishing to prevent Cercospora leaf spot on their farm should implement a 3-year crop rotation featuring non-host crops
Rotate to non-host crops (outside of the Chenopodium family) for 2-3 years
Don't plant susceptible crops in the same spot more than once every three years.
Rotate out of land where spinach was grown for at least 2-3 years
We summarise this source in our notes rather than quote a line from it.
Plants it applies to · 4
Salad & greens · 3, Roots & tubers · 1
Roots & tubers · 1
How this rule has changed
Every change is dated, newest first. The full record, with each reason, is in the data download.
- Added to the rules
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Cite this page
Milpa Gardens. “Do not plant beets, chard, spinach or amaranth in ground that held them within 3 years.” Evidence grade: Promising. https://milpa.garden/rules/do-not-plant-beets-chard-spinach-amaranth/
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How we grade evidence
- Well established
- The rule names its mechanism and is settled, by sources a person has read and checked or by plain arithmetic and geometry.
- Promising
- The mechanism is named and the literature backs it. A few questions are still open.
- A good hunch
- Plausible by its mechanism, but field studies are thin, so treat it as a lean.
- Contested
- The evidence points both ways, or no study has tested it, so the planner does not enforce it.
- Refuted
- The claim did not survive its sources. It is kept so the folklore can be answered.