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.
hardiness zone — estimated
mature spread — estimated
ph range — estimated
Rules that apply to Red Raspberry
Promising
Do not establish Verticillium-susceptible perennials (raspberries, strawberries, stone fruit) in ground that recently hosted Verticillium dahliae — either nightshades, or a logged planting of a Verticillium host (strawberry, raspberry or other bramble, or stone fruit).
costly if ignored → warn
Mechanism: Verticillium dahliae persists in soil as microsclerotia and infects a wide host range spanning nightshades and rose family. There is no in-ground cure once a susceptible perennial is planted, so it can wilt and die from inoculum an earlier host left behind — and because the reservoir family may differ from the victim's, the same-family rotation intervals miss it.
Evidence: confirmed against 3 sources in the research-based literature.
the 3 sources
Penn State Extension, 'Bramble Disease - Verticillium Wilt' (Kathy Demchak), extension.psu.edu/bramble-disease-verticillium-wilt (read 2026-07-12): 'Verticillium wilt is caused by two common soilborne fungi (Verticillium dahliae and Verticillium albo-atrum) that have a wide host range'; 'To minimize disease, choose a planting site with no known history of this problem. Avoid land recently planted with tomatoes, potatoes, eggplants, peppers, strawberries, raspberries, or stone fruits'; 'There are no effective fungicides for management once the plants are in the ground'; 'The number of years required to eliminate verticillium, especially the resting spores from the soil, is unknown.'
UMass Extension, New England Small Fruit Management Guide, 'Brambles - Diseases', ag.umass.edu/fruit/ne-small-fruit-management-guide/brambles/diseases (read 2026-07-12): 'Verticillium attacks a wide range of plants, including potatoes, tomatoes, peppers, eggplant and strawberries. It overwinters in the soil and on plant debris. Do not plant [raspberries following these crops].'; 'Non-host crops such as corn or wheat can help eliminate the fungus if grown for at least 2 years before planting raspberries.'
Host range / persistence corroborated by the source already cited on another rule here: NC State Extension, 'Verticillium Wilt of Tomato and Eggplant' (read 2026-07-11): 'The pathogen can survive in the soil without a host for up to 10 years in the form of structures called microsclerotia'; 'affects more than 300 host families.'
remedy
Site the perennial on ground with no recent nightshades, or choose one that is not Verticillium-susceptible. Extension advises growing a non-host — corn or a small grain — for at least two years first, without claiming that clears the soil. Once the perennial is planted there is no in-ground cure.
Do not establish Verticillium-susceptible perennials where the season log records that a Verticillium host (strawberry, raspberry or other bramble, or stone fruit) previously grew — a reservoir the coarse prior-nightshades family signal structurally misses.
costly if ignored → warn
Mechanism: The same reservoir as the family-level rule — Verticillium dahliae persisting in soil as microsclerotia — but recognised precisely instead of coarsely. The family-level rule fires on a prior nightshades family, which is all a manual history checkbox can express; this rule fires on the logged planting's own species carrying the verticillium_host marker, so a prior rose family host (strawberry, raspberry, stone fruit) counts while a non-host rose family like apple correctly does not — precision the family signal cannot give.
Evidence: confirmed against 3 sources in the research-based literature.
the 3 sources
Penn State Extension, 'Bramble Disease - Verticillium Wilt' (Kathy Demchak), extension.psu.edu/bramble-disease-verticillium-wilt (read 2026-07-12): 'To minimize disease, choose a planting site with no known history of this problem. Avoid land recently planted with tomatoes, potatoes, eggplants, peppers, strawberries, raspberries, or stone fruits'; 'There are no effective fungicides for management once the plants are in the ground.'
UMass Extension, New England Small Fruit Management Guide, 'Brambles - Diseases', ag.umass.edu/fruit/ne-small-fruit-management-guide/brambles/diseases (read 2026-07-12): 'Verticillium attacks a wide range of plants, including potatoes, tomatoes, peppers, eggplant and strawberries.'; 'Non-host crops such as corn or wheat can help eliminate the fungus if grown for at least 2 years before planting raspberries.'
Host range / persistence corroborated by NC State Extension, 'Verticillium Wilt of Tomato and Eggplant' (read 2026-07-11): microsclerotia survive 'up to 10 years' and the pathogen 'affects more than 300 host families.'
remedy
Site the perennial where the log shows no previous Verticillium host, or choose one that is not susceptible. Extension advises growing a non-host — corn or a small grain — for at least two years first, without claiming that clears the soil. Once the perennial is planted there is no in-ground cure.
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.
Brambles pick up viruses from other brambles: aphids carry raspberry mosaic and related viruses from wild raspberries and blackberries, and from older infected plantings, into a new one. Site a new bramble planting at least 600 feet from wild brambles, and keep it away from any bramble planting that shows virus.
suboptimal if ignored → advise
Mechanism: Aphid vectoring. The raspberry aphids that feed on wild and cultivated brambles pick up the viruses in one probe and carry them to the next plant they feed on, so any bramble within their flight is a source, and there is no cure once a cane is infected.
Evidence: confirmed against 7 sources in the research-based literature.
the 7 sources
University of Maryland Extension, 'Growing Raspberries and Blackberries in a Home Garden', extension.umd.edu/resource/growing-raspberries-and-blackberries-home-garden (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Choose a planting site at least 300 feet from wild brambles, a potential source of diseases.'
UNH Extension, 'Growing Fruits: Raspberries and Other Bramble Crops', extension.unh.edu/resource/growing-fruits-raspberries-and-other-bramble-crops-fact-sheet (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Destroy all wild bramble plants within a distance of 600 feet of the site if possible, to reduce the possibility that viruses might spread to your planting.'
UMass Extension, New England Small Fruit Management Guide, 'Brambles: Viruses', ag.umass.edu/fruit/ne-small-fruit-management-guide/brambles/viruses (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Plant your raspberries away from any wild brambles which may be harboring viruses that could be spread to your plants'; 'A distance of at least 600 feet between cultivated raspberries and any wild brambles is recommended'; 'However, some raspberry varieties are resistant to aphid feeding and are thus somewhat protected.'
Penn State Extension, 'Aphids on Raspberries in Home Gardens', extension.psu.edu/aphids-on-raspberries-in-home-gardens (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Aphids can retain the virus for several hours and are very efficient at transmitting the virus from plant to plant; a single feeding probe by a single aphid suffices'; 'The maximum distance that aphids travel is unknown, but if an aphid is picked up by a stiff breeze, it can be carried for miles'; 'Eliminate virus-infected wild and cultivated raspberries'; 'Maintain 500 to 1,000 feet between new plantings and virus-infected wild and cultivated raspberries.'
Iowa State Extension, 'Planting Raspberries in the Home Garden', yardandgarden.extension.iastate.edu/article/2013/04-12/raspberry.html (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'If possible, remove all wild brambles near the new raspberry planting to prevent the spread of disease.'
University of Illinois Extension, Hort Answers, 'Raspberry (Rubus idaeus and R. occidentalis)', web.extension.illinois.edu/hortanswers/plantdetail.cfm?PlantID=283&PlantTypeID=10 (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Plant in elevated areas away from trees and buildings, and away from wild brambles to avoid viral diseases.'
remedy
Plant certified virus-free stock at least 600 feet from wild brambles, dig out wild brambles nearer than that where you can, and if an older raspberry or blackberry planting in your garden shows mosaic-mottled leaves or crumbly fruit, take it out before planting new canes.
Raspberry and blackberry canes are biennial: a cane grows its first year (a primocane), fruits its second year (a floricane), then dies. On summer-bearing types, after harvest cut out only the spent floricanes, at ground level, and keep the current year's primocanes - they are next year's crop. Cutting every cane down on a summer-bearing plant removes next year's fruit. Ever-bearing (primocane-fruiting) types fruit on first-year canes and, grown for a single fall crop, can instead be cut wholesale close to the ground in winter.
suboptimal if ignored → advise
Mechanism: Each cane lives two years while the crown persists: a vegetative primocane in year one becomes the fruiting floricane in year two, and a floricane dies after fruiting - it will not fruit again or survive another winter. Next year's fruiting wood is therefore this year's primocanes, so removing them removes the crop. The spent floricanes are cut at ground level because dead stubs left standing can harbor canker-causing fungi.
Evidence: confirmed against 2 sources in the research-based literature.
the 2 sources
Univ. of Maryland Extension, 'Growing Raspberries and Blackberries in a Home Garden', extension.umd.edu/resource/growing-raspberries-and-blackberries-home-garden (read 2026-08-22): 'In the second growing year, those one-year-old canes, now called floricanes, produce flowers and fruit on main stems and laterals (side branches)'; 'Floricanes die after fruiting and must eventually be removed because they will not produce another harvest or survive a second winter'; 'When plants are dormant, remove the dead floricanes that fruited the previous season'; 'When removing dead, fruited canes or excess primocanes, make the cuts at ground level so that the dead stubs do not protrude where they can harbor canker-causing fungi'; 'Primocane-bearing raspberry and blackberry cultivars produce fruit on first-year canes.'
Univ. of Illinois Extension, 'Pruning and Training Raspberries', extension.illinois.edu/small-fruits/pruning-and-training-raspberries (read 2026-08-22): 'primocanes are first year growth and in second year they grow into floricanes which bear fruits'; 'Floricanes are cut after harvest'; 'Primocanes that will bear fruits the following year are thinned to avoid competition'; 'For a single late season crop harvest, canes are cut very close to the ground in December to February.'
remedy
After harvest, or while the plants are dormant, cut the canes that fruited out at ground level and leave the current primocanes standing; thin crowded primocanes so the keepers grow stout. On an ever-bearing type grown for one fall crop, cut all canes very close to the ground in winter instead.
Another 108 rules in the corpus apply by situation rather than by species — rotation intervals, frost windows, sun, spacing and soil. Read the full evidence page.
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.
