Phaseolus coccineus · legumes
Runner Bean (Phaseolus coccineus) is an annual in the legumes.
Also called Scarlet Runner Bean, Climbing Runner Bean, Dwarf Runner Bean.
The same species behaves differently by cultivar group, so the planner resolves size, timing and support against the group rather than the species.
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.
Mechanism: Ice nucleation in leaf tissue.
Evidence: settled without a trial - climatology.
Sow or set out after the last frost date, or start indoors and transplant once it has passed.
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.
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 beans root rots 3 years, white mold (Sclerotinia) 3 years, anthracnose 2 years; peas root rots 3-4 years, Fusarium wilt 4-5 years.
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.'
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.
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.
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.
Mechanism: A frost-tender crop with a long days-to-maturity cannot mature if it is only direct-sown after the last frost — the frost-free window is too short. A head start under cover buys the weeks the season lacks; the seedling is set out only once frost has passed — the transplant date is still frost-gated.
Evidence: confirmed against 2 sources in the research-based literature.
University of Minnesota Extension, 'Starting seeds indoors', extension.umn.edu/planting-and-growing-guides/starting-seeds-indoors: seed-starting chart gives tomato '5-6 weeks' and pepper and eggplant '9 weeks' before the outdoor planting date (warm crops set out after the last frost). Read 2026-07-19 (LLM-summarised); read by the maintainer 2026-07-25, which is the read that promoted this rule. Note what the corpus's per-crop values do with the sources: tomato 6 sits at the top of Minnesota's '5-6 weeks' and inside Illinois's '6-8'; pepper and eggplant 8 sit BELOW Minnesota's '9 weeks' and at the top of Illinois's '6-8'. They are a reconciliation of two published ranges, not a figure either source prints.
University of Illinois Extension, 'When should I start my seeds?' (2023-02-10), extension.illinois.edu/blogs/good-growing/2023-02-10-when-should-i-start-my-seeds: peppers, tomatoes, and eggplant started '6-8 weeks before the last frost'. Read 2026-07-19.
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.
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.'
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.
Mechanism: Warm-season legumes take up water fast at sowing (imbibition), and in cold soil that first rush of cold water injures the seed tissue before the seedling can establish - imbibitional chilling - so the seed rots or comes up damaged. Soil below about 15 C (60 F) at sowing depth is where this bites, and the frost-free date can arrive weeks before the soil is that warm.
Evidence: confirmed against 2 sources in the research-based literature.
USU Extension, 'How to Grow Beans in Your Garden', extension.usu.edu/yardandgarden/research/beans-in-the-garden (read 2026-08-14): 'Beans are warm weather vegetables that require soil and air temperatures above 60°F for best germination and plant growth'; 'If you plant when soils are below 60°F, germination is greatly reduced'; 'Seedlings will emerge in 7-10 days when planted in soil that has warmed to 65-85°F.'
UMN Extension, 'Growing beans in home gardens', extension.umn.edu/vegetables/growing-beans (read 2026-08-14): 'Bean seed planted in cold soil may rot rather than germinate, and plant growth will be very slow in cooler weather'; 'Plant beans once the soil has warmed.'
Wait for the soil to warm - about 15 C (60 F) at sowing depth, which a soil thermometer reads in a minute - or start the beans in warm cells and set them out. Peas are the opposite and are out of scope here: half-hardy, they germinate in cold soil and are sown early on purpose.
Another 107 rules in the corpus apply by situation rather than by species — rotation intervals, frost windows, sun, spacing and soil. Read the full evidence page.
Milpa Gardens. "Runner Bean (Phaseolus coccineus)." https://milpa.garden/plants/phaseolus-coccineus/
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.