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A Forager’s Year

No. 142

Butternut

Juglans cinerea

white walnut

Nut & seed nuts

Drawing: Britton & Brown, Illustrated Flora (1913)

Find
Elusive
Effort
Real work
ID risk
Beginner
Origin
native
Uses
  • Eat raw / salad
  • Baking & desserts
  • Roasted nuts

Season

  1. Jan
  2. Feb
  3. Mar
  4. Apr
  5. May
  6. Jun
  7. Jul
  8. Aug
  9. Sep
  10. Oct
  11. Nov
  12. Dec

in season peak

Picking: At least one park allows it, but it is at risk: gather nuts for planting. See Where you may pick.

What these mean

Find

1 Everywhere · 2 Common in the right habitat · 3 Patchy · 4 Elusive. This is about how much there is, not whether you may pick it. It is based on iNaturalist sightings within 25 km (about 15 miles) of downtown DC, counted on October 3, 2026. The four rules that each plant’s “Find” reason refers to: (A) the estimate is the confirmed sightings, plus the unconfirmed ones (scaled down where the plant has lookalikes in its genus), plus the sightings marked as planted; (B) the tier by estimate: 1,500 or more is tier 1, 250–1,499 tier 2, 50–249 tier 3, under 50 tier 4; (C) tier 1, Everywhere, also needs a source saying the plant is common in lawns, sidewalks, yards or gardens, vacant lots or towns, or at least one DC street tree of it per km of sidewalk, otherwise it is tier 2; (D) if a reliable source says the plant is rare in this region, or that wild plants rarely bear the harvest, only planted sightings count. iNaturalist is a website and phone app where people post photos of the plants and animals they see. A sighting is “research grade” when other users have confirmed what it is; “needs ID” sightings are not confirmed yet, and “cultivated” ones are marked as planted.

Effort

1 Grab & eat · 2 Quick kitchen prep (under about 30 minutes) · 3 Real work (hours, or cooking needed for safety) · 4 Project (days or equipment). Scored on the simplest worthwhile use; each plant’s page says why.

ID risk

How hard it is to harvest safely. Beginner: no dangerous lookalike, and the edible part is not easily confused with a toxic part. Careful: a toxic lookalike, or toxic parts that end up in the harvest unless removed (for example elderberry stems, unripe ground cherries), or other parts of the plant rated medium-or-higher toxicity, with reliable features to separate them. Expert only: a potentially deadly lookalike that is hard to separate, or (for not-recommended harvests like pokeweed) a plant whose safe preparation can’t be guaranteed. Toxic parts that are obviously separate and thrown away anyway (pits, seeds, skins) don’t raise it; the Toxic parts mark carries that warning.

Native or not, and the invader stars

Origin is where the plant comes from: native, non-native, or mixed (the harvest covers both). The stars rate plants on invasive plant lists: ★★★ Virginia DCR “High” or Maryland prohibited invasive · ★★ Virginia “Medium” · ★ Virginia “Low” · ☆ listed only by the Maryland Invasive Species Council or the Mid-Atlantic Plant Invaders guide (advisory) · no stars: native or not listed.

Seasons

Start, peak and end are given in thirds of a month: early, mid or late. A plant counts as in season for a month if it is in season at any point in that month. Some greens and roots have a second window, in spring or fall; their page shows each window. A season that runs across New Year is shown as one window.

What it looks like

A native tree of the walnut family, small to medium-sized, with long compound leaves of 11 to 19 toothed leaflets and gray bark (NC State). The fruits hang singly or in clusters of 2 to 5; each is an oblong, pointed fruit 1.5 to 2.2 inches long in a green husk with 2 to 4 lengthwise ridges, covered with short, sticky hairs (NC State; USDA Forest Service). Inside the husk is a hard, thick, deeply furrowed shell (USDA NRCS) that cracks into two halves (Forager Chef). The kernel is sweet and oily (USDA Forest Service); Forager Chef describes a smooth, mild, buttery taste, milder than black walnut, and Eat The Weeds calls butternut the best flavored of the walnuts. Butternut canker has killed most of the species' trees (University of Minnesota), and some trees that look like butternuts are hybrids with Japanese walnut; in some places the hybrids are virtually the only 'butternuts' to be found (Purdue University).

Safety

No part of butternut is named as poisonous to people in the sources checked (NC State; USDA Forest Service); early settlers used the root bark as a laxative (NC State). Juglone is most concentrated in the fruit husks and roots (USDA Forest Service), and black walnut and butternut make the most juglone of the walnut family (Government of Ontario). Wear gloves: the husks secrete a strong dye that stains clothing and skin (NC State), and handling walnut husks has caused blistering skin irritation from juglone (Cutis, a dermatology journal). Use only sound nuts: the Government of Ontario warns that walnuts with brown or black rotten husks can carry a mold toxin and are not fit to eat. Allergy: people with severe English walnut allergy will likely react to other closely related walnut species too (Journal of Allergy and Clinical Immunology), and FDA treats black, English and Japanese walnuts as major tree-nut allergens. Harmless lookalikes: black walnut, whose fruit is round rather than oblong and sticky-haired, and whose twig pith is light brown rather than dark chocolate-brown, with no band of hairs above the leaf scar (NC State; Purdue University); hybrids of butternut with Japanese walnut, which often grow close to roads, have in some cases been propagated and distributed as butternuts, and have a notch in the leaf scar and tan or pinkish bark fissures (Purdue University); English walnut, a planted tree with only 5 to 11 leaflets (NC State); and pecan and bitternut hickory, whose leaflets grow larger toward the leaf tip and whose husks split along four seams (Purdue University). Black walnut, Japanese walnut, hybrids, English walnut and pecan all have edible nuts (NC State; Purdue University); the meat of bitternut hickory nuts is very bitter (NC State). Tree-of-heaven, an invasive tree that NC State lists as often confused with butternut, has leaflets with a notched base and teeth only near the base, and NC State tags it for contact dermatitis.

Lookalikes

  • Tree-of-heaven Ailanthus altissima irritant

    Not like the nut: NC State lists tree-of-heaven and butternut as often confused with each other. Tree-of-heaven is a non-native invasive tree whose leaflets have a glandular, notched base and teeth only near the base, with smooth edges otherwise; its leaves and broken stems can smell foul, and it bears clusters of flat, twisted, winged seeds instead of nuts (NC State). NC State tags it for contact dermatitis.

  • Black walnut Juglans nigra harmless (may be edible)

    NC State lists black walnut among trees often confused with butternut. Butternut’s fruit is oblong to ovoid, with 2 to 4 lengthwise ridges on a green husk covered with short, sticky hairs (NC State); Purdue University says it is more elongated than black walnut’s round fruit. Butternut twigs have dark chocolate-brown pith and a thick band of hairs, like a moustache, above each leaf scar; black walnut has light brown pith and no moustache (Purdue University). Black walnut nuts are edible (NC State).

  • Japanese walnut and its hybrids with butternut (buartnut) Juglans ailantifolia; Juglans × bixbyi harmless (may be edible)

    Purdue University warns that some apparent butternuts are actually hybrids with Japanese walnut, which are fertile, often grow close to roads, and in some cases have been propagated and distributed as butternuts. Compared with butternut, hybrids tend to have a notch in the leaf scar, elongated lenticels, green or tan twigs and tan or even pinkish bark fissures; trees growing away from edges, towns, homes or old farm sites are the most likely to be pure butternuts (Purdue University). Nuts from hybrids are food for people and wildlife (Purdue University).

  • English walnut (Persian walnut) Juglans regia harmless (may be edible)

    NC State lists English walnut among trees often confused with butternut. English walnut leaves have 5 to 11 oblong leaflets with mostly smooth edges (NC State), against butternut’s 11 to 19 toothed leaflets (NC State), and it is a planted tree. Its nuts are edible (NC State).

  • Bitternut hickory Carya cordiformis harmless (may be edible)

    NC State lists bitternut hickory among trees often confused with butternut, and Purdue University says hickories are sometimes misidentified as butternuts. Hickory leaflets become larger toward the end of the leaf, hickory nuts sit in woody husks that split along four seams, and hickories lack the band of hairs above the leaf scar (Purdue University). Bitternut has long, scaly, yellow buds, and the meat of its nut is very bitter (NC State).

  • Pecan Carya illinoinensis harmless (may be edible)

    Purdue University says pecan trees and other hickories are sometimes misidentified as butternuts. Their leaflets become larger toward the end of the leaf, their husks split along four seams, and they lack the band of hairs above the leaf scar (Purdue University). Pecan nuts are edible (NC State).

Safety flags

Safety marks and flags: what this means

Deadly lookalike / Toxic lookalike: a cited source names a lookalike of that danger, recorded near DC (an iNaturalist sighting within 25 km, a DC street tree, or a Smithsonian listing for DC) and looking like the part you eat. Other lookalikes are still listed, marked “not recorded near DC” or as not looking like the part you eat. Deadly means a source says eating it may be fatal or calls it deadly, or NC State rates it high severity with life-threatening symptoms (sources sometimes disagree; for example Virginia creeper). Each plant’s Lookalikes list says how to tell them apart; “harmless (may be edible)” lookalikes are listed so you know a mix-up isn’t dangerous. Cook first: cooking is needed for safety (for daylilies it is a precaution, not a sourced requirement). Eat in moderation: a source says to limit quantity or frequency (for example oxalates in sorrels and dock, ginkgotoxin, safrole). Spray risk: a source says the plant is commonly treated with herbicide in parks or lawns (invasive control, lawn weeds) or, for ginkgo, sprayed to stop fruiting. Contamination: a source says the plant concentrates pollutants. Each plant’s Safety flags list gives the details and sources.

ID risk
Beginner
Why
No toxic lookalike is named. NC State and Purdue University name black walnut, English walnut, bitternut hickory, pecan and butternut hybrids with Japanese walnut as trees confused with butternut; all are harmless and most have edible nuts. Butternut’s fruit is oblong, ridged and sticky-haired, black walnut’s is round; hickories and pecan have husks that split along four seams. NC State also names tree-of-heaven, a whole-tree confusion whose fruit is a winged seed; NC State tags it for contact dermatitis.
Handling hazards
Staining hulls (serious)
Soil risk
low
ID risk: what this means

How hard it is to harvest safely. Beginner: no dangerous lookalike, and the edible part is not easily confused with a toxic part. Careful: a toxic lookalike, or toxic parts that end up in the harvest unless removed (for example elderberry stems, unripe ground cherries), or other parts of the plant rated medium-or-higher toxicity, with reliable features to separate them. Expert only: a potentially deadly lookalike that is hard to separate, or (for not-recommended harvests like pokeweed) a plant whose safe preparation can’t be guaranteed. Toxic parts that are obviously separate and thrown away anyway (pits, seeds, skins) don’t raise it; the Toxic parts mark carries that warning.

Handling hazards: what this means

Stings, thorns, irritating or phototoxic sap, staining hulls and spiny husks, with a severity: minor = brief discomfort; moderate = rash or blisters lasting days; serious = burns, scarring or medical care possible.

Soil risk: what this means

Based on the part you eat, following the urban-soil lead guidance on the Field safety page: higher for greens, shoots and roots; moderate for flowers; low for fruit, nuts and sap.

Field safety for every outing (poison ivy, ticks, soil, and more)

When to pick

Starts
mid Sep
Peak
late Sep–early Oct
Ends
late Oct

Butternuts ripen in September and October (USDA Forest Service; NC State), and Purdue University harvests them from the middle of September through October. They are ready when about half the fruits yield to finger pressure, about when the first tenth have fallen; the earliest to fall are usually wormy or shriveled (Purdue University). In Minnesota butternuts drop about a month earlier than black walnuts, and squirrels take them almost as soon as they fall (Forager Chef), so Purdue University shakes or knocks the fruits down rather than waiting. The fruit often stays on the tree until after the leaves fall (USDA Forest Service). Good crops come every 2 to 3 years (USDA Forest Service). No source gives DC dates, and the peak is an estimate.

How the dates were worked out

Every start, peak and end was re-checked in October 2026. “Sourced” means a source opened during the check states that timing for the DC or Mid-Atlantic area. “Estimated” means no source states it exactly; the reason, the evidence and the source links are under “How the dates were worked out” on each plant’s page. Peaks are often estimated, because few sources name a peak. iNaturalist evidence means research-grade sightings near DC, by month, of the plant at that stage (for example, in fruit). iNaturalist is a website and phone app where people post photos of the plants and animals they see. A sighting is “research grade” when other users have confirmed what it is; “needs ID” sightings are not confirmed yet, and “cultivated” ones are marked as planted.

Season basis: estimated: peak

Start

sourced

Peak

estimated: No source names a DC peak. Late September to early October is the middle of the mid-September to October harvest window Purdue gives; the DC black walnut peak is late September to early October, and butternut is said to drop earlier, so the peak may come at the early end.

End

sourced

Evidence

start: Purdue University (Indiana; range-wide guidance): 'Butternut seeds become mature toward the end of summer and may be harvested from the middle of September through October.' USDA Forest Service: the nut 'matures in September and October of the year of pollination'. NC State: 'They usually mature from September to October.' | peak: Purdue University: 'Butternuts, like walnuts, are harvested once 50% of the fruits are ripe (yield to finger pressure)—about the time the first 10% of the fruits have fallen.' Forager Chef (Minnesota): butternuts drop 'Typically about a month earlier than black walnuts, falling around September where I live.' iNaturalist (25 km of DC, research grade, all sightings by month): 8 in September, 3 in October. | end: Purdue University: harvest 'from the middle of September through October'. USDA Forest Service: 'The fruit usually remains on the tree until after leaf fall'.

Where to look

Rare here: look in stream valleys and floodplain woods; logged most along the C&O Canal towpath, where walnuts may be picked (1 bushel a day), and in Rock Creek Park, which is look-only. Prince William Forest Park lists only black walnuts, so butternuts are ambiguous there (ask the park); otherwise pick in Virginia state parks or from private trees with permission. Make sure the tree is a butternut and not a hybrid with Japanese walnut, and leave some nuts for planting.

Habitats
street & yard trees (planted), old fields & meadows, floodplain & stream-valley forest, upland oak-hickory woods
Habitats: what this means

Listed where the plant’s own sources place it in that habitat. “Disturbed ground & waste places” means a cited source places it on disturbed areas, sites, soil or ground, on waste places or waste ground, on construction or abandoned building sites (old home sites count), on rubble or in strip mines. When the source gives examples of the disturbed places, at least one example must be of that kind. Examples that do not count: natural or forestry disturbance (treefall gaps, fire, windthrow, flood scour, old riverbanks and creeks, clear-cuts); roadsides, railroads and rights-of-way; and abandoned fields, pastures and farmland, which are “Old fields & meadows”. “Vacant lots” only where a source says vacant or empty lots.

Most-logged places

You may pick here

  • C&O Canal NHP (towpath, Georgetown to Great Falls MD and beyond)

    4 sightings · Legal to pick: yes · see them on iNaturalist

    Legal to pick under the C&O Canal compendium (by hand, personal use, daily limit; trail-side only at Great Falls MD).

No picking here (1 place)
  • Rock Creek Park

    2 sightings · Legal to pick: no · see them on iNaturalist

    Look but don’t pick: Rock Creek Park’s compendium bans gathering any fruit, nut, berry, seed or greenery.

Most-logged places: what this means

The places with the most research-grade iNaturalist sightings within 25 km of downtown DC (re-counted in October 2026 over every named place, campuses, condominiums and private grounds included), each marked legal to pick or not. A sighting inside several named places counts once, for the smallest of them, but a sighting inside a National Park Service park never counts for a private, campus or unchecked place. iNaturalist shows where people walk and log plants, not true abundance. Private campuses, condominiums, museums, estates and utility land (Pepco’s power-line land near Sligo Creek) are marked “no” (pick only with the owner’s permission); public university campuses, city parks and other places whose picking rules were not checked (county stormwater land, the U.S. Capitol Grounds, Greenbelt’s North Woods, federal facilities such as the National Zoo) are “unknown”. A place needs at least 2 sightings, so plants with very few sightings have no places. At-risk plants (butternut, nannyberry, American chestnut, ramps, riverbank goldenrod) get places like every other plant; each page says why the plant is at risk and gives any advice its sources give. For some places, mostly Rock Creek Park, the iNaturalist map shows more sightings than the count here, because a map link cannot leave out exactly the sightings credited to another place. iNaturalist is a website and phone app where people post photos of the plants and animals they see. A sighting is “research grade” when other users have confirmed what it is; “needs ID” sightings are not confirmed yet, and “cultivated” ones are marked as planted.

Ways to use it

  • eat raw or lightly toasted: Forager Chef finds freshly cracked butternuts excellent eating
  • butternut ice cream (Eat The Weeds)
  • maple-butternut candy, popular in New England (USDA Forest Service; NC State)
  • baking: farm families used the kernels in baking (USDA NRCS)
  • harvest early, before squirrels take the nuts: gather once about half the fruits yield to finger pressure, shake or knock them from the tree, and discard the first ones to fall, which are usually wormy (Purdue University; Forager Chef)
  • harvest wearing gloves; the husks are sticky and their dye stains skin and clothing (Forager Chef; NC State)
  • cure the nuts in a single layer with air moving over them: 3 to 4 weeks with the husks on, or about 2 weeks with them taken off (Forager Chef)
  • shell, after curing, by knocking off the dried husk and striking the nut squarely on end on a hard surface; butternuts split into two halves (Forager Chef)

Keeping

Cure 2 to 4 weeks with air moving over them, then store in the shell in a cool, dark place, or crack and freeze the kernels, since the nuts can turn rancid quickly.

Use within
months+
Keeps fresh
Spread the fruits in a single layer with air moving over them and cure them, 3 to 4 weeks with the husks on or about 2 weeks with them off (Forager Chef). Cured nuts keep a long time in the shell in a cool, dark, dry place; Forager Chef has kept dried butternuts for years. The nuts are oily and can turn rancid quickly (NC State; University of Minnesota).
Keeping basis
specific to this plant

Ways to keep it

  • Freeze as researched: freeze; canning: n/a (not shelf-canned)

    Freeze shelled kernels in plastic bags; frozen black walnut kernels keep almost indefinitely (Iowa State; general guidance for walnuts), and butternuts can turn rancid quickly (NC State).

  • Store whole as researched: store in shell; canning: n/a (not shelf-canned)

    Cure fully, then keep in the shell in a cool, dark place; dried butternuts have lasted for years in a garage (Forager Chef).

Canning: what this means

Shelf-stable canning, three levels. Lab-tested: a lab-tested recipe from the National Center for Home Food Preservation (NCHFP) or Oregon State covers this fruit and product, or a generic recipe for its kind (the line says so, for example chokeberry). Extension recipe: a published Extension recipe (University of Alaska Fairbanks, written for Alaska species; University of Maine’s dandelion jelly), or a process that is safe only with a pH meter; follow it exactly, never improvise. No tested recipe: refrigerate or freeze, don’t can. “Hot-bottled syrup” = maple and walnut syrup, which keep when bottled hot at full syrup density. The Canning line names the exact product each source covers, for example “whole berries” or “juice”; a product not named there (such as juice from a berry with only a whole-berry recipe) has no tested recipe.

Keeping basis: what this means

“Specific to this plant” or “general guidance for its type” (for example NCHFP guidance for leafy greens applied to a wild green).

Nutrition

Not researched: in October 2026, only the calendar’s plants of the month and chicory leaves were researched.

Native or not

Butternut hybridizes freely with Japanese walnut, an introduced tree; the hybrids (Juglans × bixbyi, called buarts or buartnuts) are fertile, and in some places they or their offspring are virtually the only butternuts to be found (Purdue University).

Origin
native
Native range
eastern & central United States and southeastern Canada
Virginia invasive rank
not listed
Maryland invasive status
not listed
Native or not, and the invader stars: what this means

Origin is where the plant comes from: native, non-native, or mixed (the harvest covers both). The stars rate plants on invasive plant lists: ★★★ Virginia DCR “High” or Maryland prohibited invasive · ★★ Virginia “Medium” · ★ Virginia “Low” · ☆ listed only by the Maryland Invasive Species Council or the Mid-Atlantic Plant Invaders guide (advisory) · no stars: native or not listed.

Virginia DCR, Virginia Invasive Plant Species List (effective September 2024), verbatim: "Under the DCR Invasive Species Assessment Protocol, approved by the Virginia Invasive Species Working Group, January 2024, species were ranked as exhibiting high, medium or low levels of invasiveness based on their threat to natural communities and native species. Invasiveness rank is higher for species that: • Alter ecosystem processes, such as succession, hydrology or fire regime. • Are capable of invading undisturbed natural communities. • Cause substantial impacts on rare or vulnerable species or natural communities or high-quality examples of more common communities. • Are found widely distributed and generally abundant where present. • Disperse readily to new areas. • Are difficult to control." The list also states: "The list is for educational purposes only and has no regulatory authority."

Maryland Department of Agriculture, Maryland Prohibited Invasive Plant Law and Regulations page, verbatim: "Plants on the Maryland Prohibited Invasive Plant List may not be added to stock after the effective date and should not be sold after their phase-out period ends."

No official DC invasive plant list was found.

How the ratings were set

Find
Elusive Estimate 25 = 21 research-grade iNaturalist sightings within 25 km + 49 needs-ID sightings counted at 1.7% (21 of the 1,206 research-grade Juglans sightings here are butternut) + 3 'cultivated' (planted) sightings (rule A); that is tier 4 by count (rule B). Rule D (scarce here): the Digital Atlas of the Virginia Flora says "Infrequent to rare throughout" about butternut in Virginia, and adds that large healthy trees are now rare. So only its planted sightings count: 3, which is tier 4. Final tier 4.
Effort
Real work Beat the squirrels to the ripe fruits, glove up, cure them 2 to 4 weeks, then knock off the dried husks and crack each nut on end with a hammer into two halves (Forager Chef; Purdue University).
Find: what this means

1 Everywhere · 2 Common in the right habitat · 3 Patchy · 4 Elusive. This is about how much there is, not whether you may pick it. It is based on iNaturalist sightings within 25 km (about 15 miles) of downtown DC, counted on October 3, 2026. The four rules that each plant’s “Find” reason refers to: (A) the estimate is the confirmed sightings, plus the unconfirmed ones (scaled down where the plant has lookalikes in its genus), plus the sightings marked as planted; (B) the tier by estimate: 1,500 or more is tier 1, 250–1,499 tier 2, 50–249 tier 3, under 50 tier 4; (C) tier 1, Everywhere, also needs a source saying the plant is common in lawns, sidewalks, yards or gardens, vacant lots or towns, or at least one DC street tree of it per km of sidewalk, otherwise it is tier 2; (D) if a reliable source says the plant is rare in this region, or that wild plants rarely bear the harvest, only planted sightings count. iNaturalist is a website and phone app where people post photos of the plants and animals they see. A sighting is “research grade” when other users have confirmed what it is; “needs ID” sightings are not confirmed yet, and “cultivated” ones are marked as planted.

Effort: what this means

1 Grab & eat · 2 Quick kitchen prep (under about 30 minutes) · 3 Real work (hours, or cooking needed for safety) · 4 Project (days or equipment). Scored on the simplest worthwhile use; each plant’s page says why.

Sources

39 sources, each linked to the original.

  1. Pass the Walnut Syrup? (excerpt from The Sugarmaker’s Companion by Michael Farrell) Chelsea Green PublishingBacks up: picking rules
  2. List of Rare, Threatened, and Endangered Plants of Maryland (March 2026) Maryland Department of Natural Resources, Wildlife and Heritage ServiceBacks up: picking rules
  3. Natural Heritage Resources of Virginia: Rare Plants (September 2026) Virginia Department of Conservation and Recreation, Division of Natural HeritageBacks up: picking rules
  4. Rock Creek Park Superintendent’s Compendium (2026) National Park ServiceBacks up: picking rules
  5. C&O Canal NHP Superintendent’s Compendium, effective September 11, 2026 National Park Service, Chesapeake and Ohio Canal NHPBacks up: picking rules
  6. National Capital Parks-East 2026 Superintendent’s Compendium National Park ServiceBacks up: picking rules
  7. Prince William Forest Park Superintendent’s Compendium National Park Service, Prince William Forest ParkBacks up: picking rules
  8. 4VAC5-30-50. Flowers, plants, minerals, etc. Virginia Law Library (law.lis.virginia.gov)Backs up: picking rules
  9. 36 CFR 2.1 - Preservation of natural, cultural and archeological resources Legal Information Institute, Cornell Law School (text of federal regulation)Backs up: picking rules
  10. Maryland man fined $50 for picking berries ReasonBacks up: picking rules
  11. Butternut (Silvics of North America) USDA Forest ServiceBacks up: description, habitat, season, uses, safety
  12. Juglans cinerea (Butternut, Lemon Nut, Oil Nut, White Walnut) NC State Extension Gardener Plant ToolboxBacks up: description, habitat, season, uses, safety, keeping, safety details
  13. Plant Guide: Butternut, Juglans cinerea L. USDA NRCS (National Plant Data Center)Backs up: description, habitat, uses, safety, picking rules
  14. Identification of Butternuts and Butternut Hybrids (FNR-420-W; Farlee, Woeste, Ostry, McKenna and Weeks) Purdue Extension and USDA Forest Service Hardwood Tree Improvement and Regeneration CenterBacks up: description, safety, native or invasive status, safety details
  15. Butternuts / White Walnuts (Alan Bergo, 2020, updated 2023) Forager ChefBacks up: description, season, uses, storage, keeping
  16. Butternut - Juglans cinerea University of Minnesota Urban Forestry Outreach & ResearchBacks up: description, storage, keeping
  17. Black Walnuts and Butternut (Green Deane) Eat The WeedsBacks up: description, uses
  18. iNaturalist research-grade observations of Juglans cinerea within 25 km of downtown DC iNaturalistBacks up: findability
  19. Annotated Checklist of the Vascular Plants of the Washington-Baltimore Area, Part I (Shetler & Orli, 2000) Smithsonian Institution, National Museum of Natural History, Department of BotanyBacks up: habitat
  20. Juglans cinerea (Fire Effects Information System, Coladonato 1991) USDA Forest Service, Rocky Mountain Research StationBacks up: habitat
  21. Juglans cinerea L. (Butternut, White Walnut) Digital Atlas of the Virginia Flora (Virginia Botanical Associates)Backs up: habitat, findability
  22. Conservation and Management of Butternut Trees (FNR-421-W; Farlee, Woeste, Ostry, McKenna and Weeks) Purdue Extension and USDA Forest Service Hardwood Tree Improvement and Regeneration CenterBacks up: habitat, season, uses, safety, picking rules, native or invasive status, safety details
  23. USDA PLANTS Database: Juglans cinerea (JUCI), native status USDA NRCSBacks up: native or invasive status
  24. Virginia Invasive Plant Species List (effective date: September 2024) Virginia Department of Conservation and Recreation, Division of Natural HeritageBacks up: native or invasive status
  25. Maryland Prohibited Invasive Plant Law and Regulations (Maryland Prohibited Invasive Plant List, updated January 2026; additions effective July 15, 2026; 'Next Plants To Be Assessed' 2026-2027) Maryland Department of Agriculture, Plant Protection & Weed ManagementBacks up: native or invasive status
  26. Non-Native Invasive Terrestrial Plant Species in the State of Maryland (updates approved through the April 18, 2024 MISC meeting) Maryland Invasive Species CouncilBacks up: native or invasive status
  27. Plant Invaders of Mid-Atlantic Natural Areas, Field Guide (Swearingen & Fulton, 2022; successor to the NPS/USFWS 5th ed., 2017) Mid-Atlantic Invasive Plant Council / Passiflora Press (hosted by Bugwood/Mid-Atlantic Invaders Tool)Backs up: native or invasive status
  28. Invasive Plants in the District DC Department of Energy & EnvironmentBacks up: native or invasive status
  29. IgE binding to and cross-reactivity among English walnut and other walnut (Juglans) species (Comstock, McGranahan, Peterson and Teuber; abstract, Journal of Allergy and Clinical Immunology, 2004) Journal of Allergy and Clinical Immunology (University of California, Davis authors), via EM consulteBacks up: safety, effort & ID risk, safety details
  30. Walnut toxicity Government of Ontario (Ministry of Agriculture, Food and Rural Affairs content)Backs up: safety, safety details
  31. Discoloration and Bullous Lesions on the Hands (Photo Challenge; Cutis 104(4), October 2019) Cutis (peer-reviewed dermatology journal)Backs up: safety, safety details
  32. Questions and Answers Regarding Food Allergen Labeling (Edition 5): Guidance for Industry, January 2025 U.S. Food and Drug AdministrationBacks up: safety, safety details
  33. Juglans nigra (Black Walnut) NC State Extension Gardener Plant ToolboxBacks up: safety, safety details
  34. Juglans regia (English Walnut) NC State Extension Gardener Plant ToolboxBacks up: safety, safety details
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  38. iNaturalist month-of-year histogram of research-grade butternut observations within 25 km of downtown DC iNaturalistBacks up: season
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