Elderberry (Sambucus canadensis)

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.

Rules that apply to Elderberry

Well established

Hardiness zone is the correct variable for perennials, and only for perennials.

suboptimal if ignored → advise

Mechanism: Zones encode average annual minimum winter temperature, which governs whether a woody perennial survives to spring. It is the wrong quantity for an annual, which never sees winter. THE CEILING IS A SECOND AND DIFFERENT MECHANISM, and until 2026-07-26 this rule enforced it without naming it. A zone too WARM does not kill a perennial; it fails to chill it. Deciduous fruit crops need a winter dormancy period to break bud and set fruit, so in a zone milder than a plant is adapted to it may survive and never crop. Until ISSUES #13 was decided the band was enforced at both ends; now (option E) only the cold end gates — it alone follows from the definition of the zone system — and the warm end is carried as an ADVISORY, not a refusal. AND THE WARM END IS A CULTIVAR'S ANSWER, NOT A SPECIES', which is the honest limit of what this rule can do. Chill requirement is published per variety and varies enormously within a species, so a species-level ceiling says "the modelled range does not reach your zone", never "no plant of this kind will crop for you". So the engine offers the plant above its band and advises choosing a cultivar rated for the zone rather than refusing it — the same move invariant 3 makes for soil, applied to chill.

Evidence: confirmed against 3 sources in the research-based literature.

the 3 sources

THE FLOOR IS TRUE BY DEFINITION and needs no citation: the USDA system defines a zone AS a band of average annual minimum winter temperature, so 'a plant colder-hardy than your zone survives your winter' is the definition restated. This rule was `verified_trivially` on that basis alone until 2026-07-26. THE CEILING WAS NEVER COVERED BY IT - a minimum-temperature definition says nothing about a plant failing for want of chill - and that gap is why ISSUES #13 exists. The pointer below closes it.

OSU Extension EC 1303, 'Growing blackberries in your home garden' (Bernadine Strik), catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/ec1303.pdf (read 2026-07-26). THE CEILING'S MECHANISM, STATED: 'Winter cold-hardy cultivars adapted to the colder regions of Oregon (such as zones 5 to 7), may not grow normally in regions of the Willamette Valley (zone 8) where winters are warmer and plants receive less winter chill.' A plant failing in a WARMER zone for want of chill - which is what this rule's upper bound enforces and what no source said until now. THE SAME PAGE MAKES IT A CULTIVAR PROPERTY: 'Even cultivars within the same type (trailing, erect or semierect) differ in fruit quality and flavor, appearance, tolerance to pests, cold hardiness, and plant longevity', and the remedy it gives is the one this rule's rejection text now repeats: 'Minimize risk by choosing types and cultivars that are adapted to your hardiness zone.' The page then publishes a table of sixteen cultivars EACH WITH ITS OWN ZONE RANGE, which is the strongest available evidence that a species-level band is an approximation. [read]

WHAT THIS DOES NOT SETTLE. The mechanism is now named, but the corpus still carries ONE band per species where the source carries one per cultivar, and 12 of 25 perennial zones have no citation at all. So the ceiling is explained without being precise. ISSUES #13 stays open on that, and the rejection text is deliberately phrased as 'the modelled range does not reach your zone' rather than as a prediction that nothing will crop.

Read the full rule → · open in the planner ↗

Well established

Elderberries must be cooked before eating. Raw or unripe berries - and all leaves, stems and roots - are toxic; only fully ripe, cooked berries are safe.

suboptimal if ignored → advise

Mechanism: The plant holds cyanogenic glycosides, highest in the unripe fruit, leaves, stems and roots and lower in ripe fruit. Eaten raw they release cyanide in the gut and cause nausea, vomiting and diarrhoea; cooking ripe berries drives off and inactivates the compound, which is why cooked elderberry (syrup, wine, jelly) is a traditional food while the raw plant is not.

Evidence: confirmed against 2 sources in the research-based literature.

the 2 sources

NC State Extension Gardener Plant Toolbox, 'Sambucus canadensis', plants.ces.ncsu.edu/plants/sambucus-canadensis/ (fetched in-container 2026-08-31; READ BY THE MAINTAINER 2026-09-01): Poison Severity 'Low'; Poison Symptoms 'Ingestion can cause nausea, vomiting, diarrhea, coma. Unripe fruits are much more toxic than fully ripe fruits. Cooking helps inactivate the cyanogenic glycoside.'; Poison Toxic Principle 'Cyanogenic glycoside and alkaloid'; Poison Parts 'Fruits, Leaves, Roots, Stems'. [read]

UMN Extension, 'Elderberries the safe way' (Cottage Food Connection), extension.umn.edu/about/our-stories/news/cottage-food-connection/elderberries-the-safe-way (READ BY THE MAINTAINER 2026-09-01): 'Raw elderberries, including the stems, leaves, seeds and flowers, contain naturally occurring compounds that can release cyanide during digestion'; and the cooking fix: 'Cooking elderberries significantly reduces the risk, making properly prepared jams, syrups, and other cooked products safe to enjoy' - 'Boil the elderberries for at least 10 minutes.' A second extension source agreeing verbatim with NC State on the hazard, the parts and the cooking fix. [read]

remedy

Eat only fully ripe berries, and only after cooking. Never eat raw berries, unripe green berries, or any leaves, stems or roots.

Read the full rule → · open in the planner ↗

Another 91 rules in the corpus apply by situation rather than by species — rotation intervals, frost windows, sun, spacing and soil. Read the full evidence page.

Elderberry

What the corpus records

Which of these numbers are soft

Rules that apply to Elderberry

Hardiness zone is the correct variable for perennials, and only for perennials.

Elderberries must be cooked before eating. Raw or unripe berries - and all leaves, stems and roots - are toxic; only fully ripe, cooked berries are safe.