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A Forager’s Year

No. 86

Butternut

Juglans cinerea

white walnut

Fruit half-grown green fruits, husk and all, before the shell forms (pickled or steeped in liquor)

Drawing: Britton & Brown, Illustrated Flora (1913)

Find
Elusive
Effort
Quick kitchen prep
ID risk
Beginner
Origin
native
Uses
  • Pesto & sauces
  • Jam & jelly
  • Syrup & cordial
  • Wine & spirits
  • Pickles

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: The rules are unclear. Ask the park. It is at risk: Butternut is on Maryland’s rare-plant list, which ranks it between imperiled and vulnerable (S2S3) (Maryland DNR). 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

The young fruit of butternut, a native tree of the walnut family with long compound leaves of 11 to 19 toothed leaflets (NC State). The fruits hang singly or in clusters of 2 to 5, each oblong and pointed in a green husk with 2 to 4 lengthwise ridges and short, sticky hairs (NC State); Forager Chef warns that green butternuts are very sticky. They are picked young, about the size of a small ping-pong ball, straight from the tree, while a paring knife still cuts easily through them, and the whole fruit is used, husk and all (Forager Chef; Hank Shaw). Forager Chef has used green butternuts and recommends black walnuts or butternuts for the strongest aroma, and Hank Shaw says any walnut works for pickling. Pickled walnuts are an old English food, which Hank Shaw describes as fairly soft, puckery and strangely floral. Butternut canker has killed most of the species' trees (University of Minnesota), and some trees that look like butternuts are hybrids with Japanese walnut (Purdue University).

Safety

The green husk is eaten along with the rest of the young fruit, and it contains juglone; black walnut and butternut produce the most juglone of the walnut family (Government of Ontario). The University of Washington Botanic Gardens' library says all walnut species have edible properties and that pickled walnuts, eaten as an occasional snack rather than in large quantities, are no cause for concern; anyone sensitive to walnuts should avoid them. Allergy: people with severe English walnut allergy will likely react to other closely related walnut species too (Journal of Allergy and Clinical Immunology). Wear gloves: the juice stains hands for a week or more (Backyard Forager; Hank Shaw), and handling walnut husks has caused blistering skin irritation from juglone that needed a doctor’s care (Cutis, a dermatology journal). No part of butternut is named as poisonous to people in the sources checked (NC State); early settlers used the root bark as a laxative (NC State). 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 green fruit: 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
early Jun
Peak
mid Jun–late Jun
Ends
early Jul

Pick while a paring knife or needle passes easily through the whole fruit; once the shell starts to form inside, it is too late (Forager Chef; Backyard Forager; Hank Shaw). Butternut flowers from April to June (NC State). The perfect unripe nut typically comes in mid-June in the Midwest (Forager Chef); the traditional pickling date in England is late June (Hank Shaw), or June 15 (University of Washington Botanic Gardens). Do not use green fruits from the ground, which the tree has dropped (Forager Chef). No source gives DC dates, so the dates here are estimates: test each tree.

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: start, peak, end

Start

estimated: No source dates the start for the DC area or for butternut alone. Early June is placed a little before the mid-June Midwest timing, since DC’s season usually runs earlier, and matches the black walnut green-fruit estimate.

Peak

estimated: No source gives a DC peak; mid to late June is the range of the dates given for the Midwest and England.

End

estimated: No source dates shell hardening in butternut; early July is the end used for black walnut green fruit (shell hardening in early July in a Missouri study), with the knife test deciding for each tree.

Evidence

start: NC State: 'Bloom time is from April to June.' Forager Chef (Midwest): 'There’s a window for harvesting the perfect unripe nut ( typically mid-June here in the Midwest where I am )'. University of Washington Botanic Gardens: 'Traditionally, walnuts for pickling were harvested June 15'. | peak: Forager Chef: 'typically mid-June here in the Midwest'. Hank Shaw: 'the traditional harvest date in England is late June'. University of Washington Botanic Gardens: harvested June 15. | end: Forager Chef: 'if you hit resistance, you’re too late-try again next year.' Hank Shaw: 'Once that shell forms inside the walnut’s hull, you’re too late'. Backyard Forager: the walnuts must be young enough not to have developed a hard shell beneath the green husk.

Where to look

Rare here: the same trees as the fall nut harvest, in stream valleys and floodplain woods; logged most along the C&O Canal towpath and in Rock Creek Park. Green walnuts are ambiguous on the C&O Canal, at the listed National Capital Parks-East sites, in Prince William Forest Park and in Virginia state parks (ask the park first); Rock Creek Park is look-only. Otherwise pick from private trees with the owner’s permission, and make sure the tree is a butternut and not a hybrid with Japanese walnut.

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

None of the most-logged places allows picking.

Ask first: rules unclear or not checked

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

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

    Ambiguous: the C&O compendium allows walnuts (1 bushel per person per day) but does not say whether unripe green walnuts picked from the tree count; ask the park first.

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

  • pickled walnuts: prick the whole green fruits, brine them for 8 days, leave them a day in the sun until they turn black, then pack them in jars under a hot pickling liquid and wait at least a month (Hank Shaw)
  • nocino, a dark walnut liqueur: steep the quartered green fruits in high-proof alcohol for 40 days, strain, sweeten and let it age for months (Backyard Forager)
  • walnut jam or preserves: peel the young nuts, prick them, soak them in water, then simmer them in a heavy syrup (Forager Chef)
  • walnut ketchup, a sour, punchy sauce like steak sauce (Forager Chef)
  • harvest straight from the tree, not from the ground, while a paring knife still cuts easily through the fruit (Forager Chef)
  • harvest and cut the fruits wearing gloves: the juice stains hands for a week or more (Backyard Forager; Hank Shaw)

Keeping

Start the brine or the infusion soon after picking, using only fresh, firm fruit; keep the finished pickles in the refrigerator.

Use within
within a few days
Keeps fresh
Fresh green walnuts are not kept: start the brine or the infusion soon after picking, and use only fresh, firm fruit free of spoilage (general guidance for pickles, NCHFP). Forager Chef refrigerates green walnuts, or keeps them as cool as possible, until he uses them. Hank Shaw’s pickled walnuts, kept cool, last a year.
Canning
no tested recipe: refrigerate or freeze, don’t can
Keeping basis
general guidance for its type

Ways to keep it

  • Infuse as researched: infuse/vinegar; canning: n/a (not shelf-canned)

    Nocino: steep the quartered fruits in high-proof alcohol for 40 days in a cool, dark place, strain, mix with an equal amount of sugar syrup, let it sit three months and bottle it; the flavor improves over the next six months (Backyard Forager).

  • Pickle as researched: pickle; canning: no tested recipe — refrigerator pickle only

    Hank Shaw brines the pricked fruits for 8 days, sun-dries them a day until black, packs them under a hot pickling liquid and keeps the jars below 70°F, in the fridge or a basement, for at least a month before eating. No tested home-canning recipe for pickled walnuts was found, and NCHFP says to use only recipes with tested proportions of ingredients, so keep the jars in the refrigerator.

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
Quick kitchen prep Test each fruit with a knife or needle, then glove up and prick the fruits for brine (about 30 minutes of work) or quarter them into alcohol; the rest is waiting: 8 days in brine and a month in the jar for pickles (Hank Shaw), or 40 days of steeping for nocino (Backyard Forager).
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

38 sources, each linked to the original.

  1. List of Rare, Threatened, and Endangered Plants of Maryland (March 2026) Maryland Department of Natural Resources, Wildlife and Heritage ServiceBacks up: picking rules
  2. Natural Heritage Resources of Virginia: Rare Plants (September 2026) Virginia Department of Conservation and Recreation, Division of Natural HeritageBacks up: picking rules
  3. Rock Creek Park Superintendent’s Compendium (2026) National Park ServiceBacks up: picking rules
  4. C&O Canal NHP Superintendent’s Compendium, effective September 11, 2026 National Park Service, Chesapeake and Ohio Canal NHPBacks up: picking rules
  5. National Capital Parks-East 2026 Superintendent’s Compendium National Park ServiceBacks up: picking rules
  6. Prince William Forest Park Superintendent’s Compendium National Park Service, Prince William Forest ParkBacks up: picking rules
  7. 4VAC5-30-50. Flowers, plants, minerals, etc. Virginia Law Library (law.lis.virginia.gov)Backs up: picking rules
  8. 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
  9. Maryland man fined $50 for picking berries ReasonBacks up: picking rules
  10. Butternut - Juglans cinerea University of Minnesota Urban Forestry Outreach & ResearchBacks up: description
  11. Juglans cinerea (Butternut, Lemon Nut, Oil Nut, White Walnut) NC State Extension Gardener Plant ToolboxBacks up: description, habitat, season, safety, safety details
  12. 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
  13. Cooking with Green Walnuts (Alan Bergo, 2022, updated 2023) Forager ChefBacks up: description, uses, season, safety, storage, keeping
  14. Pickled Walnuts (Hank Shaw, 2014, updated 2022) Hunter Angler Gardener Cook (Hank Shaw)Backs up: description, uses, season, storage, keeping
  15. iNaturalist research-grade observations of Juglans cinerea within 25 km of downtown DC iNaturalistBacks up: findability
  16. Butternut (Silvics of North America) USDA Forest ServiceBacks up: habitat
  17. 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
  18. Juglans cinerea (Fire Effects Information System, Coladonato 1991) USDA Forest Service, Rocky Mountain Research StationBacks up: habitat
  19. Plant Guide: Butternut, Juglans cinerea L. USDA NRCS (National Plant Data Center)Backs up: habitat, picking rules
  20. Juglans cinerea L. (Butternut, White Walnut) Digital Atlas of the Virginia Flora (Virginia Botanical Associates)Backs up: habitat, findability
  21. 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, safety, picking rules, native or invasive status, safety details
  22. USDA PLANTS Database: Juglans cinerea (JUCI), native status USDA NRCSBacks up: native or invasive status
  23. Virginia Invasive Plant Species List (effective date: September 2024) Virginia Department of Conservation and Recreation, Division of Natural HeritageBacks up: native or invasive status
  24. 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
  25. 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
  26. 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
  27. Invasive Plants in the District DC Department of Energy & EnvironmentBacks up: native or invasive status
  28. On the safety of pickled walnuts (Plant Answer Line) University of Washington Botanic Gardens, Elisabeth C. Miller LibraryBacks up: safety, season, safety details
  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. Juglans nigra (Black Walnut) NC State Extension Gardener Plant ToolboxBacks up: safety, safety details
  33. Juglans regia (English Walnut) NC State Extension Gardener Plant ToolboxBacks up: safety, safety details
  34. Carya illinoinensis (Hardy Pecan, Pecan) NC State Extension Gardener Plant ToolboxBacks up: safety, safety details
  35. Carya cordiformis (Bitternut Hickory) NC State Extension Gardener Plant ToolboxBacks up: safety, safety details
  36. Ailanthus altissima (Tree of Heaven) NC State Extension Gardener Plant ToolboxBacks up: safety, safety details
  37. General Information on Pickling National Center for Home Food Preservation (University of Georgia)Backs up: storage, keeping
  38. Foraged Nocino: a Delicious Liqueur Made from Unripe Nuts (Ellen Zachos, 2018) Backyard ForagerBacks up: uses, season, safety, storage, keeping