How we grade evidence
Every rule this planner runs on carries one of five words that say how sure we are of it. The word sits beside the rule wherever it appears, on a plant page, a plant team or in the planner, and it links to this page. Here is what each word commits to.
- Well established 31 rules
- The rule names its mechanism and is settled, by sources a person has read and checked or by plain arithmetic and geometry.
- Promising 84 rules
- The mechanism is named and the literature backs it. A few questions are still open.
- A good hunch 22 rules
- Plausible by its mechanism, but field studies are thin, so treat it as a lean.
- Contested 2 rules
- The evidence points both ways, or no study has tested it, so the planner does not enforce it.
- Refuted 4 rules
- The claim did not survive its sources. It is kept so the folklore can be answered.
These counts are rules. The 35 bits of garden folklore we check are graded with the same words, counted on their own: 21 Contested, 14 Refuted. See them all in Folklore, checked.
Two things to know about a grade
A rule is graded “Well established”, “Promising” or “A good hunch” only if it can say, in one sentence, how it works, and the top two never lean on the word “helps”. A claim that only correlates is downgraded or dropped.
Whether a person has checked a rule against its sources is a second mark, said on every rule’s page right beside its grade. 132 of the 143 rules were checked against a source by a person, 8 were settled by arithmetic, geometry or a definition, and 2 are waiting for a person to read a source. The model that helped write these rules isn’t allowed to verify its own work.
Of the 323 sources the rules cite, 292 are university extension guides, 12 are peer-reviewed studies and 19 are government and other publications. Extension guides are written by university specialists from the research, so they are good sources, but they are a step away from the trials themselves: 4 of the 107 source-checked rules graded Well established or Promising cite a study directly.
Where the grades live
Each rule page shows its grade, how it works, its sources and how it has changed. The whole graded set is one file you can download and keep, and how this is built explains why the graded rules are the product and the app is their front end. The things we are least sure of have their own page.