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A Forager’s Year

No. 63

Chinese chestnut

Castanea mollissima

Nut & seed nuts

Drawing: American chestnut, Britton & Brown, Illustrated Flora (1913)

Find
Patchy
Effort
Quick kitchen prep
ID risk
Careful
Origin
non-native
Safety marks
  • Deadly lookalike
Uses
  • Eat raw / salad
  • Flour
  • 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

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.

Safety marks and flags

Deadly lookalike / Toxic lookalike: a cited source names a lookalike of that danger. 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.

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 medium tree, about 40 feet, from China. It bears spiny burs 2-3 inches across that split to release usually 2-3 glossy brown nuts. The nuts are crisp, meaty and sweet, though less sweet than the American chestnut. Unlike most nuts they are starchy, more like a potato than an oily nut.

Safety

Toxic lookalike: horse chestnut (Aesculus hippocastanum, often planted) and the buckeyes (Aesculus) are highly poisonous. NC State lists aesculin and aescin, with vomiting, paralysis and stupor, and says they may be fatal. Tell them apart by the leaves. True chestnuts have simple, toothed leaves set one at a time along the twig. Aesculus has palmately compound leaves with 5-7 leaflets radiating from one point. A true chestnut’s bur is densely covered in sharp bristles. A horse chestnut’s is a leathery capsule with sparse spines, smooth between them. Nut count is not reliable because sources disagree. Handle burs with leather gloves. Discard moldy nuts.

Lookalikes

Safety flags

Safety marks and flags: what this means

Deadly lookalike / Toxic lookalike: a cited source names a lookalike of that danger. 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
Careful
Why
Lookalike horse chestnut and buckeyes (Aesculus) are highly poisonous and may be fatal. Separate them by leaves: true chestnuts have simple toothed leaves set singly; Aesculus has palmately compound leaves of 5-7 leaflets. Chestnut burs are densely covered in sharp bristles; Aesculus husks are leathery with sparse spines, smooth between them ('like a spiny golf ball', TACF).
Handling hazards
Spiny husks (minor)
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–late Sep
Ends
late Oct

Chinese chestnuts ripen from mid or late September through October (NC State Extension); Virginia DOF lists September. The crop falls over 2 to 4 weeks, and the nuts put on half their weight in the last two weeks, so let them fall on their own and gather every few days (Oregon State Extension). Burs that have not split usually hold blank nuts (Oregon State). The late-September peak is an estimate from DC iNaturalist records.

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 peak; late September is where the DC iNat records and the Virginia date overlap.

End

sourced

Evidence

start: NC State Extension: ripens in mid or late September through October. Virginia DOF: matures first year, September. | peak: DC iNaturalist fruiting records by third of the month (days 1-10, 11-20, 21-end): September 0/3/4, October 2/2/0, then 1 in early November (18 records in all, including green burs in July-August and one in February). Virginia DOF lists September. Oregon State: the crop falls over 2-4 weeks in September and October. | end: NC State: ripens through October. Oregon State: nuts ripen in September and October. The last DC iNaturalist fruiting record is in early November.

Where to look

Planted in yards, old orchards and some parks; logged trees along the Mount Vernon Trail near Dyke Marsh are in a no-picking park, and Wolf Trap allows chestnuts (one gallon a day) though none are logged there, so look for spiny bur litter under yard trees and ask the owner.

Habitats
street & yard trees (planted)
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)

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

    Ambiguous: the C&O compendium allows edible fruits, nuts and berries generally but sets no limit for this one; ask the park first.

No picking here (4 places)
  • Mount Vernon Trail

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

    Look but don’t pick: GW Memorial Parkway sites (incl. Great Falls VA, Theodore Roosevelt Island, Dyke Marsh) designate nothing for gathering.

  • Rock Creek Park

    5 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.

  • Woodend Nature Sanctuary (Audubon Naturalist Society)

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

    Private property: pick only with the owner’s permission.

  • Meadowbrook Local Park

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

    Look but don’t pick: Montgomery/Prince George’s parks (M-NCPPC) ban harvesting vegetation without a permit.

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 (rugosa rose) have no places. No most-logged places are named for at-risk plants (ramps, chinquapin, American chestnut); chinquapin’s page names Mason Neck State Park, where picking is legal, and asks you to leave most nuts. 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, boiled or baked (NC State Extension)
  • Roast: cut an X or slit in the shell first so the nuts don’t burst, then roast at 375 F for 20-25 minutes or in a wok (Oregon State Extension)
  • Boil: simmer 30 minutes and the shell and skin come off easily (Oregon State Extension)
  • Dry until rock-hard and grind into chestnut flour, or rehydrate later (Oregon State Extension)
  • Storage: fresh chestnuts are perishable. Refrigerate soon after harvest (about 2 months in the shell) or freeze; at room temperature they usually mold within 2 weeks. A few days at room temperature sweetens them, but refrigeration does the same slowly (Oregon State Extension)

Keeping

Refrigerate the nuts within a day or two of gathering (they mold in about 2 weeks at room temperature), and freeze or dry them for longer keeping.

Use within
within a few days
Keeps fresh
Perishable: chestnuts are high-starch and high-moisture, more like a potato than a nut. Refrigerate soon after harvest: about 2 months in the shell in the fridge (OSU), or a few weeks in a ventilated plastic bag (Missouri). They mold within about 2 weeks if left out of the fridge. Cure at room temperature 3-5 days before roasting for sweetness (Missouri).
Keeping basis
specific to this plant

Ways to keep it

  • Dry as researched: dry/dehydrate; canning: n/a (not shelf-canned)

    Dry them rock-hard, as for walnuts, for long-term storage; grind into flour or rehydrate by soaking (OSU).

  • Dry as researched: roast & store; canning: n/a (not shelf-canned)

    Cut an X in each shell and roast at 375-425°F for 20-25 minutes; eat roasted nuts soon (OSU; Missouri).

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

    Seal raw nuts in a non-ventilated bag for year-round use; about 1 year at 0°F (Missouri; OSU).

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

Origin
non-native
Native range
East Asia (China to North Korea)
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
Patchy Estimate 157 = 68 research-grade iNaturalist sightings within 25 km + 182 needs-ID sightings counted at 23% (68 of the 294 research-grade Castanea sightings here are Chinese chestnut) + 47 'cultivated' (planted) sightings (rule A); that is tier 3 by count (rule B). Rule D does not apply: the National Park Service’s species list for Rock Creek Park marks it rare in that park, but a single park’s list is not a statement about the region. Final tier 3.
Effort
Quick kitchen prep Score an X in each shell and roast 20-25 minutes, or simmer 30 minutes and peel; drying for chestnut flour is a 3.
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

25 sources, each linked to the original.

  1. Rock Creek Park Superintendent’s Compendium (2026) National Park ServiceBacks up: picking rules
  2. 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
  3. Maryland man fined $50 for picking berries ReasonBacks up: picking rules
  4. Wolf Trap National Park for the Performing Arts, Compendium of Regulatory Provisions (2026 ver. 6/5/2026) National Park Service, Wolf Trap National Park for the Performing ArtsBacks up: picking rules
  5. Update on latex allergy: New insights into an old problem (World Allergy Organization Journal, 2021) PubMed Central (NIH/NLM)Backs up: effort & ID risk
  6. iNaturalist research-grade observations of Castanea mollissima within 25 km of downtown DC iNaturalistBacks up: findability
  7. NPSpecies record: Castanea mollissima in Rock Creek Park (ROCR) National Park Service (IRMA NPSpecies)Backs up: habitat
  8. NPSpecies record: Castanea mollissima in George Washington Memorial Parkway (GWMP) National Park Service (IRMA NPSpecies)Backs up: habitat
  9. UFA Street Trees (DC Urban Forestry street-tree inventory), Castanea records District of Columbia (DDOT Urban Forestry Division, via DC GIS)Backs up: habitat
  10. Purchasing and Roasting Chestnuts for the Holidays University of Missouri Integrated Pest ManagementBacks up: keeping
  11. USDA PLANTS Database: Castanea mollissima (CAMO83), native status USDA NRCSBacks up: native or invasive status
  12. Virginia Invasive Plant Species List (effective date: September 2024) Virginia Department of Conservation and Recreation, Division of Natural HeritageBacks up: native or invasive status
  13. 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
  14. 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
  15. 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
  16. Invasive Plants in the District DC Department of Energy & EnvironmentBacks up: native or invasive status
  17. Aesculus hippocastanum (horsechestnut) NC State Extension Gardener Plant ToolboxBacks up: safety
  18. Chestnut oaks, beeches, and horsechestnuts The American Chestnut FoundationBacks up: safety
  19. Wild Edibles of Missouri (Jan Phillips) Missouri Department of ConservationBacks up: safety details
  20. Aesculus flava (Yellow Buckeye) NC State Extension Gardener Plant ToolboxBacks up: safety details
  21. Chinese chestnut research-grade observations within 25 km of DC, by month (fruiting annotation) iNaturalistBacks up: season
  22. Acorn and Nut Identification Guide (Forestry Topic 60, Sept 2026) Virginia Department of ForestryBacks up: season, description
  23. Castanea mollissima (Chinese chestnut) NC State Extension Gardener Plant ToolboxBacks up: season, description, uses, habitat, native or invasive status
  24. Castanea, chestnut (Woody Plant Seed Manual, Agriculture Handbook 727) USDA Forest ServiceBacks up: season, habitat
  25. Harvesting, Handling, and Storing Nuts from the Home Orchard (FS 146, rev. 2013) Oregon State University Extension Service (PDF hosted by UC ANR)Backs up: season, uses, safety, description, storage, keeping