Don't plant a crop that can't mature before your frost-free season ends
As recorded: A species must reach maturity within the site's frost-free window.
Well established A person has checked it against its sources. If you skip this, the planting fails. The planner won’t allow it.
How it works
The season's accumulated growing degree days (a running total of its warmth) against the total the crop needs to mature, or the crop's days to maturity against the number of frost-free days.
What to do about it
Start it indoors and transplant it, choose a variety with fewer days to maturity, or skip this crop at this site.
The evidence
Evidence: checked against 3 sources in the research-based literature.
The 3 sources
Once you know the average dates of the last frost in spring and the first frost in fall, count the number of days between. If the “days to maturity” figure for a desired vegetable is a larger number of days and the “frost tolerance” column indicates “none,” the sad truth is that particular vegetable probably won’t grow to maturity.
Check the seed packet for the number of days until maturity so that there will be enough time for plants to grow before the first killing frost.
… high elevation areas don’t accumulate enough “growing degree units” (GDUs, also called growing degree days and heat units) to support some of the most coveted warm season vegetables
Where this rule stops
Frost-tender annual and biennial crops, as its Montana State source scopes it (a crop whose "frost tolerance" column says "none"). A hardy or half-hardy crop's window is another rule's.
See the other rule: Hardy crops can go in later, counted back from the freeze they can't stand
Plants it applies to · 34
Fruiting vegetables · 14, Beans & peas · 5, Flowers · 5, Herbs · 4, Salad & greens · 3, Cover crops & soil builders · 2, Roots & tubers · 1
Fruiting vegetables · 14
+6 moreShow fewer
Beans & peas · 5
Herbs · 4
Salad & greens · 3
Roots & tubers · 1
Read next
- Understanding your frost datesYour last and first frost dates are the clock the whole garden runs on. What they mean, why they're a probability, and how they decide when each crop can go out.
- How to read a planting calendarA planting chart that says "sow in April" is wrong for most of the country. The skill worth having is reading any calendar as an offset from your own frost dates. Here's how, at both ends of the season.
How this rule has changed
Every change is dated, newest first. The full record, with each reason, is in the data download.
- Details updated
- Details updated
- Sources updated
- A person read the sources and confirmed it
- Details updated
- Wording made clearer
- Added to the rules
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Cite this page
Milpa Gardens. “Don't plant a crop that can't mature before your frost-free season ends.” Evidence grade: Well established. https://milpa.garden/rules/species-reach-maturity-within-site-s-frost/
A garden planner built on graded evidence. 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.
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How we grade evidence
- Well established
- The rule names its mechanism and is settled, by sources a person has read and checked or by plain arithmetic and geometry.
- Promising
- The mechanism is named and the literature backs it. A few questions are still open.
- A good hunch
- Plausible by its mechanism, but field studies are thin, so treat it as a lean.
- Contested
- The evidence points both ways, or no study has tested it, so the planner does not enforce it.
- Refuted
- The claim did not survive its sources. It is kept so the folklore can be answered.