Do not plant brassicas in ground that held brassicas within 4 years (extension recommends 4-7, and even that is not a cure).
Promising · costly if ignored → warn
How it works
Plasmodiophora brassicae forms thick-walled resting spores that survive in soil more than 10 years. They germinate in wet, acidic soil (pH < 7); liming above ~7.2 suppresses infection. Spores outlast any garden rotation, so a host-free break reduces but does not clear inoculum.
What to do about it
Plant brassicas in different ground, or wait at least 4 years — extension recommends 4 to 7. Rotation alone is not a cure: the resting spores outlast it, and raising soil pH above ~7.2 suppresses infection.
How much it matters: Extension recommends long rotations away from brassicas — 4-7 years (NC State), 5-7 (UMass), "at least 7 years" (Cornell) — but notes this is "not guaranteed to prevent disease." The realistic levers are soil pH (lime to >7.2) and resistant cultivars; rotation is complementary.
The evidence
Evidence: confirmed against 3 sources in the research-based literature.
the 3 sources
NC State Extension, 'Clubroot of Brassicas', content.ces.ncsu.edu/clubroot-of-brassicas (read 2026-07-11): 'Plasmodiophora brassicae is capable of surviving in the soil for more than 10 years by producing thick-walled, resting spores'; 'Infested fields should be rotated away from brassica for a minimum of 4-7 years, but this is not guaranteed to prevent disease'; 'Liming to raise soil pH to 7.[2]'.
Cornell Vegetables, 'Clubroot of Crucifers', vegetables.cornell.edu/pest-management/disease-factsheets/clubroot-of-crucifers (read 2026-07-11): 'the pathogen survives for many years even in the absence of host crops'; 'rotation of at least 7 years out of susceptible crucifers may be effective.'
UMass Extension, 'Brassicas, Clubroot', ag.umass.edu/vegetable/fact-sheets/brassicas-clubroot (read 2026-07-11): 'Long (5-7 years) rotations between brassica crops'; 'Maintain a high pH by regular applications of lime.'
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.
- corpus: another rule here says what to do about a brassica rotation (remedy)
- corpus: another rule here says what to do about a brassica rotation (remedy)
- promote to verified — Brassicaceae clubroot rotation
- cite clubroot sources; interval was below the extension floor, add pH lever
Cite this page
Milpa Gardens. "Do not plant brassicas in ground that held brassicas within 4 years (extension recommends 4-7, and even that is not a cure)." Evidence grade: Promising. https://milpa.garden/rules/do-not-plant-brassicas-ground-that-held/
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.