How we source, write and correct plant information

Which sources we accept

Plant facts come from public botanical, government and institutional sources. Each stored fact keeps the source it came from, that source's tier for that kind of fact, and the date the source page was last read. Nothing is published without one.

A source is authoritative for particular kinds of fact, never for everything, so sources are tiered by what they are being used for:

• Tier A, primary and reference. The body that defines or measures the fact: the World Checklist of Vascular Plants and IPNI for accepted names, authorities, synonyms and families; USDA PLANTS for US native, introduced and noxious status; the 2023 USDA Plant Hardiness Zone Map for zones; NOAA 1991–2020 climate normals for frost and freeze dates; EPPO for pest names and hosts; USPTO for plant patents; ASPCA Animal Poison Control and Pet Poison Helpline for pet toxicity; peer-reviewed literature.
• Tier B, institutional horticulture. Research-based guidance from public institutions: university cooperative extension services, botanic gardens, USDA NRCS plant guides, US Forest Service records, and state invasive-species councils.
• Tier C, expert bodies and award programs. Horticultural societies, trial and award programs, and the trait descriptions inside plant patents, which are the breeder's own claims.
• Tier D, commercial. Nurseries, breeders and seed catalogs, used only for availability, trade names and breeder-reported specifications, and always labeled as such.
• Never evidence. Wikipedia prose, other care sites, blogs, forums, social media and AI output. Wikidata is used to match records across databases, never as evidence for a fact.
• Two citations count as two sources only when neither republishes the other, so a county page reprinting another extension's fact sheet counts once.
• Where a value depends on place, the place is shown with the value: a bloom month or a zone edge reported for North Carolina is labeled as such.
• Source pages are read within the limits their publishers set. We follow each site's robots file and terms, identify ourselves in the request, and never work around a block.

How well a fact has to be supported

Every published fact carries an evidence grade. The grade is computed from that fact's citations rather than chosen by hand, and it decides how the fact appears on the page.

• Established: two or more independent tier A or B sources agree, or one tier A source that defines the field, such as the checklist that fixes a botanical name. Shown plainly, with its footnotes.
• Supported: one tier A or B source, with nothing contradicting it. Shown with the note "1 source".
• Reported: only tier C or D sources. Shown as "Breeder-reported" or "Reported by" the publisher, so you can weigh it for yourself.
• Sources differ: tier A or B sources disagree beyond the tolerance for that kind of value. Both values are shown, each attributed to the source that gives it. Nothing is averaged and no source is quietly dropped.
• Not documented by major sources: no acceptable source was found. The field says exactly that. It never becomes a guess, and it never becomes a reassurance.
• Care facts need at least one tier A or B source. Safety facts need more: a reassuring value, such as non-toxic or edible, is stated only when independent sources agree on it.
• Numbers are compared with a tolerance before a disagreement is declared: overlapping height or pH ranges are published as their union, and hardiness zones only one source claims are shown as a note rather than folded into the headline range.

The toxicity rule

Toxicity is the highest-stakes information on this site, so it follows a precautionary rule rather than a majority rule: one credible tier A or B source reporting toxicity outweighs any number of sources that report the plant as harmless. ASPCA Animal Poison Control and Pet Poison Helpline are both used, alongside extension records.

Cats and dogs are shown separately, and the question is never left blank. A plant entry says one of five things:

• Toxic to cats / Toxic to dogs — independent sources report toxicity.
• Toxic to cats (1 source) — one tier A or B source reports it. It is published with the warning, labeled as resting on a single source, and queued for a person to check.
• Toxic to cats: sources differ — sources disagree. The page shows the warning and names both sides, because the safer reading wins.
• Non-toxic to cats — independent sources agree that no toxicity is recorded. One source is never enough to say this.
• Not documented by major sources — no cited record was found. It does not mean the plant is harmless.
• The toxic compound is named where a source names it, and reported symptoms are described in our own words. Severity is shown only where a source states it, and is never embellished.
• Edibility follows the same logic: unless a reliable source confirms that a part is edible and how it must be prepared, the page does not say it is.
• Pages about toxicity carry no shopping links of any kind, so nothing on them is written to sell you something.
• Nothing on this site is veterinary or medical advice. If you suspect poisoning, contact a veterinarian or a poison control service immediately.

Citation, not duplication

Source material is used as evidence, not as content. A fact is stored together with the sentence from the source that supports it. That stored sentence is internal evidence and is never published: what you read is our own wording and our own structure.

Facts are footnoted where they are used, and the footnotes gather into a References list at the end of the page, with one entry per source page. An entry names the publisher, links the page, and gives the date it was last read, in the form: NC State Extension Gardener Plant Toolbox. https://plants.ces.ncsu.edu/… Accessed 22 September 2026.

ASPCA and Pet Poison Helpline entries are stored as a classification with a link, and their clinical wording is paraphrased rather than reproduced. We don't republish source articles, and we don't present another publisher's text as ours. If a source asks us to change or remove an attribution, we act on it.

AI-assistance disclosure

AI tools draft and structure the prose on plant pages. Each of those pages says so, in a "How this page was made" block that also carries the date the page's facts were last checked against their sources. Readers are entitled to know how the pages they rely on were made.

AI is never the source of a fact, and the software is built so that it cannot be:

• Facts are gathered first, each with a source URL and the exact sentence that supports it. Nothing is drafted until they exist.
• Code, not a language model, checks each citation: it fetches the page, follows redirects, stores the final URL, and requires the supporting sentence to appear there word for word. Where the value can be parsed — a number with units, a zone range, a pH, a range of months — code also checks that it matches the sentence.
• Code, not a language model, grades the evidence, compares sources and applies the rules above when they disagree.
• Every drafted sentence records which facts it rests on, and is then checked against them. A sentence that its facts don't support is rewritten or removed.
• Safety facts are researched twice, independently, and the citations from both passes are merged before the fact is graded.
• Where a source cannot be checked automatically, because it blocks automated access or its terms allow reading only by a person, the fact goes to a manual verification queue. Until someone opens the page and records what it says, the field reads "Not documented by major sources". A fact waiting in the queue is never published as a guess.
• A fact published on a single safety source is queued for the same manual check, and keeps its "1 source" label until that check is done.
• AI is not used to write citations, references or source quotations, and it never writes a link to a merchant.
• No page names a human reviewer, because no named person reviews pages today. Such a line would have to name a real person and the review they actually carried out, and the build refuses to render one without that record, so there is no line.

Corrections

Email contact@opengrowguide.com with the page, the figure and your source. Corrections are handled before other mail. Changes are reflected in the page's "Last updated" date.

• Safety-relevant reports (toxicity, edibility, chemical use) come first. While one is being checked, the disputed statement is removed or marked as under review.
• A mistake is traced back to what caused it — the source, the rule or the template — and fixed there, so the same mistake is corrected everywhere it appears rather than on one page.
• Typo and formatting fixes are made without a note.

Updates

Nothing on this site is rewritten on a schedule. Pages are re-checked when we rerun the checks against their sources, and safety facts are re-checked first. A source that has changed or vanished sends its fact back for research, and the value it supported is downgraded or removed rather than left standing.

The "Facts checked" date on a page is the day its cited facts were last confirmed against those sources. It is a separate date from "Last updated", which is the day the page's wording last changed.

Independence from affiliate programs

Money reaches Open Grow Guide in one way only: affiliate commission. Pages have places for links to nurseries, seed companies and garden retailers, and such a link is built into a page only once that program has approved this site. Where one appears, the page says so above it. There are no ads on this site.

No company can pay to be included, to change care advice, to alter a toxicity entry, or to be recommended. Which plants we cover and what we say about them is decided before any merchant is considered, and toxicity pages carry no links at all. Commercial relationships are explained in the affiliate disclosure.