Do not plant the carrot family in ground that held it within 3 years.
Promising · costly if ignored → warn
How it works
The carrot leaf blights (Alternaria dauci, Cercospora carotae and the bacterial blight) and celery's Septoria late blight survive on crop debris and die as it decomposes; a break of two to three years starves them. Alternaria radicina, the black-rot species, infects celery, celeriac, dill, fennel, parsley and parsnip as well, and can persist in soil for up to eight years, which is why the family rotates as one.
What to do about it
Plant carrot-family crops in different ground, or wait until 3 years have passed since this ground last held them. Clear and turn in the old tops promptly either way, and buy clean seed: all three carrot blights ride on seed.
How much it matters: UMass: 3-4 years for carrot Alternaria leaf blight; Cornell's rotation table: carrot leaf blights 2-3 years, celery leaf blights 2 years; Clemson: three years the minimum for any family.
The evidence
Evidence: confirmed against 5 sources in the research-based literature.
the 5 sources
UMass Extension, 'Carrot, Alternaria Leaf Blight', umass.edu/agriculture-food-environment/vegetable/fact-sheets/carrot-alternaria-leaf-blight (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Practice relatively long rotations of 3-4 years'; 'A. radicina infects celery, celeriac, caraway, dill, fennel, parsley, and parsnips'; 'The fungus survives in the soil on crop debris but dies when the residue decomposes'; A. radicina 'can persist in soil for up to 8 years.'
Cornell Vegetables, 'Carrot Leaf Blight Diseases and their Management', vegetables.cornell.edu/pest-management/disease-factsheets/carrot-leaf-blight-diseases-and-their-management (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'it is important to practice a minimum of a 2-year rotation out of carrots to allow time for decomposition of crop residue'; 'All three pathogens can be transmitted through infected or contaminated seeds and can survive on crop residue, which can act as a source of inoculum in subsequent cropping years.'
Cornell Vegetables, 'Do Rotations Matter within Disease Management Programs?', vegetables.cornell.edu/pest-management/disease-factsheets/do-rotations-matter-within-disease-management-programs (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): its rotation table gives carrot leaf blights (fungal and bacterial) 2-3 years and celery leaf blights 2 years.
UMass Vegetable Notes 2025 vol. 37:13, Septoria late blight of celery, umass.edu/agriculture-food-environment/vegetable/newsletters/vegetable-notes/vegetable-notes-2025-vol-3713 (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'The pathogen survives in crop debris in soil for up to 18 months, or outbreaks may originate from seed-borne inoculum.'
Clemson HGIC, 'Crop Rotation', hgic.clemson.edu/factsheet/crop-rotation (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'a crop should only be grown in the same spot a maximum of once every three years'; its family table puts carrot, parsley, celery, cilantro, fennel and dill in the parsley family (Apiaceae).
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 - the carrot family rotates on a 3-year interval (verified) (O133 step 7, family 2)
Cite this page
Milpa Gardens. "Do not plant the carrot family in ground that held it within 3 years." Evidence grade: Promising. https://milpa.garden/rules/do-not-plant-carrot-family-ground-that/
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.