Every number above carries a confidence tier. These are the ones the corpus does not stand behind — estimated from general knowledge, or contested between sources. They are shown because hiding them would be the dishonest half of showing the rest.
bloom window — estimated
Rules that apply to Crimson Clover
Promising
Do not plant legumes in ground that held legumes within 3 years; the root rots build where they repeat, and the worst of them outlast any garden rotation.
costly if ignored → warn
Mechanism: Bean and pea root rots (Fusarium solani, Rhizoctonia, Pythium, Aphanomyces) and white mold (Sclerotinia sclerotiorum) survive in soil as spores and sclerotia and build where legumes follow legumes; a three-year break holds the common ones down. Fusarium needs longer, and Aphanomyces oospores and white mold's sclerotia persist for many years, so rotation reduces but cannot clear them.
Evidence: confirmed against 4 sources in the research-based literature.
UMN Extension, Fruit and Vegetable News, 'Crop planning deep dive: Mind your Peas and Beans' (2021), blog-fruit-vegetable-ipm.extension.umn.edu/2021/04/2021-consideration-minding-your-peas.html (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Rotate away from legumes for more than 3 years'; 'More than 6 years is needed for some diseases (Fusarium, some damping off pathogens).'
UConn IPM, 'Molds and Mildews of Beans in Connecticut', ipm.cahnr.uconn.edu/molds-and-mildews-of-beans-in-connecticut (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): white mold - 'Rotate away from susceptible crops for 7 years', it affects beans and 'practically all vegetable crops'; downy mildew - 'Rotate with other crops for 2 years.'
NDSU Agriculture, 'Field Pea and Lentil Root Rot Risk, Diagnosis and Resources', ndsu.edu/agriculture/ag-hub/field-pea-and-lentil-root-rot-risk-diagnosis-and-resources (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Fields with a long history of pulses in close rotations (every 2-3 years) are at greatest risk'; 'Chickpea, soybean, and faba bean are not susceptible to Aphanomyces euteiches and thus can be included in a rotation with pea and lentil to break up the disease cycle.'
remedy
Plant legumes in different ground, or wait until 3 years have passed since this ground last held them. Where root rot has shown, make it longer, and keep the ground draining freely: every one of these rots is worse in wet soil.
Cold-hardy annuals can be sown or transplanted before the last spring frost — hardy crops about three weeks before, half-hardy about two weeks before. Tender crops wait for the frost itself.
suboptimal if ignored → advise
Mechanism: Cold hardiness. Hardy crops tolerate hard frost and half-hardy crops tolerate light frost, so they can occupy the ground weeks before frost-tender crops are allowed in. The offset is measured from the last spring frost.
Evidence: confirmed against 4 sources in the research-based literature.
the 4 sources
University of Illinois Extension, 'Time Your Vegetable Plantings by Cold Hardiness' (2018-03-26), extension.illinois.edu/blogs/ilriverhort/2018-03-26-time-your-vegetable-plantings-cold-hardiness: very hardy vegetables 'withstand freezing temperatures and hard frosts without injury' (planted earliest in spring); frost-tolerant vegetables 'can withstand light frosts, but not freezing temperatures' (planted a couple of weeks later). LLM-summarised from a read of the page; it establishes the CATEGORIES but states no week offsets.
Colorado State Univ. Extension, GardenNotes #720, 'Vegetable Planting Guide', extension.colostate.edu/resource/vegetable-planting-guide (read 2026-07-25): hardy vegetables go in 'As early as 2-4 weeks before the date of the average last spring frost'; semi-hardy 'As early as 0-2 weeks before the date of the average last spring frost'; tender from seed 'around the date of the average last spring frost'; very tender 'Typically 2+ weeks after'. This is the source that states the offsets in weeks.
Where this rule sits in that range: hardy at 3 weeks is mid-range of CSU's 2-4. Half-hardy at 2 weeks is the EARLIEST EDGE of CSU's 0-2 - the most aggressive planting CSU sanctions, not the middle of it. The rule is inside published guidance at both ends, but it leans early on the half-hardy side and a gardener following it in a cold spring is taking that boundary.
Do not import an offset from another publication's hardiness scheme without checking the category names: CSU has no 'very hardy' tier, so a '4-6 weeks before frost' figure written against a four-tier scheme does not describe CSU's 'hardy'. Categories are not comparable across sources.
A legume fixes atmospheric nitrogen only in symbiosis with rhizobia specific to its cross-inoculation group; ground with no recent history of that group may carry too few of them to nodulate well.
suboptimal if ignored → advise
Mechanism: Nitrogen fixation happens in root nodules formed by Rhizobium or Bradyrhizobium bacteria specific to each legume group. On ground that has not grown that legume group before - a new bed, a soil-less mix, a long gap in the rotation, a fumigated or strongly acid soil - the matching strain can be absent or sparse, so nodulation and fixation are reduced until a population builds.
Evidence: confirmed against 1 source in the research-based literature.
the source
Penn State Extension, 'Inoculation of Forage and Grain Legumes', extension.psu.edu/inoculation-of-forage-and-grain-legumes (read 2026-08-14): 'Rhizobia bacteria are fairly specific as to which legumes they will infect, form nodules on the roots of, and for which they will fix nitrogen'; 'Legumes effectively nodulated by the same Rhizobia species are termed cross-inoculation groups'; 'Inoculation is recommended when the legume being planted has not been grown in that field in the past three years or with every planting of a high-value crop'; 'Inside the nodule, an enzyme called nitrogenase drives the N fixation reaction.'
remedy
On first-time legume ground, coat the seed at sowing with the inoculant matched to the crop's group (garden peas and beans, soybean, and clover each take a different one). Ground that has grown that legume recently usually needs none. It is a cheap one-time step - advised where the history is absent, never required.
Another 110 rules in the corpus apply by situation rather than by species — rotation intervals, frost windows, sun, spacing and soil. Read the full evidence page.
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.
