Do not plant beets, chard, spinach or amaranth in ground that held them within 3 years.
Promising · costly if ignored → warn
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: confirmed against 7 sources in the research-based literature.
the 7 sources
Cornell Vegetables, 'Cercospora Leaf Spot of Table beet', vegetables.cornell.edu/pest-management/disease-factsheets/cercospora-leaf-spot-of-table-beet (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Rotate with non-host crops for at least 3 years'; 'Cercospora beticola can survive in the soil on infested plant residues for up to 3 years'; hosts 'Table beet, sugar beet, spinach, Swiss chard, lambsquarters, and pigweed.'
Penn State Extension, 'Cercospora Leaf Spot on Table Beets', extension.psu.edu/cercospora-leaf-spot-on-table-beets (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Beet growers wishing to prevent Cercospora leaf spot on their farm should implement a 3-year crop rotation featuring non-host crops'; 'Cercospora beticola can overwinter on host debris and in the soil for up to 3 years or survive on alternative weed hosts like lambsquarters and pigweed'; 'Cercospora leaf spot will infect spinach, Swiss chard, and sugar beets.'
UMass Extension, 'Cercospora Leaf Spot of Swiss Chard, Beets, and Spinach', umass.edu/agriculture-food-environment/vegetable/fact-sheets/cercospora-leaf-spot-of-swiss-chard-beets-spinach (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Rotate to non-host crops (outside of the Chenopodium family) for 2-3 years'; 'It can survive in the soil for up to two years.'
Univ. of Maryland Extension, 'Cercospora Leaf Spot of Vegetables', extension.umd.edu/resource/cercospora-leaf-spot-vegetables (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Don't plant susceptible crops in the same spot more than once every three years.'
UMass Extension, 'Spinach Downy Mildew', umass.edu/agriculture-food-environment/vegetable/fact-sheets/spinach-downy-mildew (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Rotate out of spinach for at least 3 years'; 'P. farinosa is capable of producing oospores, thick-walled structures which are capable of survival in soil.'
Cornell Vegetables, 'Spinach Downy Mildew', vegetables.cornell.edu/pest-management/disease-factsheets/spinach-downy-mildew (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Rotate out of land where spinach was grown for at least 2-3 years'; 'The pathogen can survive a few years in soil as oospores'; 'Oospores also could be left behind in soil after planting contaminated seed.'
Cornell Vegetables, 'Do Rotations Matter within Disease Management Programs?' (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): its rotation table gives beet Cercospora leaf spot 3 years, beet root rots 3 years, spinach downy mildew and white rust 2 years.
Plants this fires on
Change history
Every change to this rule is one commit. This is what the project's version history records — the date and the reason — not a summary of it.
- rules: another rule here - beet, chard, spinach and amaranth rotate on a 3-year interval (verified) (O133 step 7, family 3)
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/
A garden-planning corpus: every claim states its evidence grade and links its sources on the page. Cite it with the grade, and add the date you read it.