Some seed will not germinate straight from the packet: it carries a built-in dormancy that a pre-sow treatment has to break first. A hard-coated seed is scarified or soaked so water can get in; a seed with internal dormancy is cold-moist stratified - chilled damp for weeks - before it will come up. The treatment has to be started far enough ahead of the sowing date to finish in time.
Promising · suboptimal if ignored → advise
How it works
A hard, water-impermeable seed coat holds the seed dormant by blocking imbibition, so nicking, abrading, or soaking the coat is what lets water reach the embryo; a seed with physiological dormancy stays shut until a period of cold, moist chilling lets its germination-inhibiting hormones dissipate - so each treatment takes its own span of time, and starting it late leaves the seed still dormant at sowing.
What to do about it
Check the plant's page for the treatment it needs. Scarifying (nick, abrade, or a hot-water/acid treatment) and soaking are done right before sowing; cold-moist stratification takes weeks, so start it well ahead - about six weeks before the intended sowing date is a safe general lead, though the exact period is species-specific and is on each plant's page. Fall-sowing outdoors lets winter do the chilling for hardy natives.
How much it matters: No per-species figure is invented in this rule - stratification periods run from about a month to three months depending on the seed, and each plant's own seed_treatment carries its detail. The six-week lead is a conservative planning default, not a claim about any one species; the rule advises and never blocks, because whether and how long to pre-treat is the gardener's own step.
The evidence
Evidence: confirmed against 2 sources in the research-based literature.
the 2 sources
Penn State Extension / Tianna DuPont, 'Seed and Seedling Biology', extension.psu.edu/seed-and-seedling-biology (updated January 14, 2025; fetched in-container 2026-09-20, read 2026-09-20): 'Seeds might have a hard or thick seed coat (physical dormancy). This can be broken by soaking or scarifying (scratching the surface) the seed'; and on imbibition, 'The seed rapidly takes up water and the seed coat swells and softens.'
UW-Madison Extension, Wisconsin Horticulture / Bruce Spangenberg, 'Plant Dormancy a Dependable Process', hort.extension.wisc.edu/plant-dormancy-a-dependable-process (fetched in-container 2026-09-20, read 2026-09-20): 'A tough seed coat prevents water uptake and seed germination'; 'Seeds collected from native plants are often recommended to be mixed with abrasive sand or even roughened with a file; this breaks physical dormancy'; and on cold stratification, 'After exposure to a certain length of winter cold, abscisic acid levels dissipate in seeds', with 'Typically, minimum temperatures range from upper thirties to 40 degrees Fahrenheit.'
Where this rule stops
A STANDING SEED-STARTING ADVISORY (trigger.kind always, universal like another rule here/115), cited by the germination guide and surfaced on the Why page. It gates nothing. It DRIVES one Calendar reminder: a "begin cold-stratification" task placed trigger.stratify_lead_days (42) days before a stratifying species' sow date, the number read from this rule's trigger the way another rule here reads its offset - a single default reminder, with the exact per-species period on the plant's page rather than invented per crop here. Scarify and soak need no dated task (they are done at sowing); they surface as a note on the sow task and on the plant page.
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): promote to verified — maintainer read the sources (2026-09-20)
Cite this page
Milpa Gardens. "Some seed will not germinate straight from the packet: it carries a built-in dormancy that a pre-sow treatment has to break first. A hard-coated seed is scarified or soaked so water can get in; a seed with internal dormancy is cold-moist stratified - chilled damp for weeks - before it will come up. The treatment has to be started far enough ahead of the sowing date to finish in time." Evidence grade: Promising. https://milpa.garden/rules/some-seed-will-not-germinate-straight-from/
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.