No. 64
Plant of the month: January
Common hackberry
Celtis occidentalis
Fruit ripe fruit (thin flesh; whole fruit traditionally pounded)
Drawing: Britton & Brown, Illustrated Flora (1913)
- Find
- Common in the right habitat
- Effort
- Grab & eat
- ID risk
- Beginner
- Origin
- native
- Uses
- Eat raw / salad
- Jam & jelly
- Spice & seasoning
- Dried fruit & leather
Season
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- 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.
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 hemp family (formerly placed in the elm family) with warty, corky-ridged bark and lopsided, toothed leaves that often carry little nipple galls. It bears pea-size drupes, borne singly, that ripen orange-brown to deep purple. They have a thin layer of sweet, date-like flesh over a large hard seed. Mostly a nibble, but one that lasts into winter.
Safety
No toxicity is reported in the sources checked (NC State; Lady Bird Johnson Wildflower Center). The seed is very hard, so take care with your teeth unless you are grinding it.
- ID risk
- Beginner
- Why
- No toxic lookalike is named; common hackberry and sugarberry are used the same way.
- 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.
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 Sep
- Peak
- late Sep–late Oct
- Ends
- late Feb
Towson University (Maryland) says the fruit typically ripens in September and can be foraged through the winter. USDA NRCS and the Forest Service give September to October ripening, with fruit staying on the tree for several months, sometimes until spring, and NC State agrees. Missouri Conservation describes the berries hanging on the tree all winter as a nibble for hikers. Ripe fruit is deep purple (Towson; NC State).
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 Sep to late Oct is the ripening window given by USDA, after which the fruit hangs on the tree.
End
sourced
Evidence
start: Towson University Glen Arboretum (Maryland): 'Fruit typically ripens in September but can be foraged throughout the winter'. NC State: 'It ripens in September'. | peak: USDA NRCS: fruit 'ripening in September and October, but remaining on the tree for several months'. USDA Forest Service Silvics: 'The seed ripens in September and October'. | end: Towson (Maryland): 'can be foraged throughout the winter'. NC State: 'often remains on the tree through the winter'. Silvics: 'sometimes remaining on the tree until the following spring'. MDC Wild Edibles: 'The purplish-black berries do dangle on the tree all winter and provide a welcome nibble to passing hikers.'
- Common Hackberry Towson University, Glen Arboretum
- Celtis occidentalis NC State Extension Plant Toolbox
- Common Hackberry (Celtis occidentalis) Plant Fact Sheet USDA NRCS Plant Materials Program
- Silvics of North America: Hackberry USDA Forest Service
- Wild Edibles of Missouri (Jan Phillips) Missouri Department of Conservation
Where to look
Potomac floodplains (logged most on the C&O Canal towpath and along Four Mile Run) and planted as a tough street tree; the C&O Canal allows edible fruits generally but sets no limit for hackberry, so it is ambiguous there (ask the park); otherwise pick in Virginia state parks or from private trees with permission.
- Habitats
- street & yard trees (planted), old fields & meadows, woods edges, trailsides & thickets, floodplain & stream-valley forest
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)
Ambiguous: the C&O compendium allows edible fruits, nuts and berries generally but sets no limit for this one; ask the park first. Of these, 3 are at Carderock.
No picking here (4 places)
- Four Mile Run stream valley (Arlington/Alexandria)
Look but don’t pick: Arlington County park rules (flora shall not be removed or disturbed) and Alexandria’s permit rule both apply.
- Tuckahoe Park
Look but don’t pick: Arlington County park rules say flora shall not be removed or disturbed.
- Barcroft Park
Look but don’t pick: Arlington County park rules say flora shall not be removed or disturbed.
- Theodore Roosevelt Island
Look but don’t pick: GW Memorial Parkway sites (incl. Great Falls VA, Theodore Roosevelt Island, Dyke Marsh) designate nothing for gathering.
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.
Where you may pick
C&O Canal NHP’s compendium says edible fruits, nuts and berries may be gathered by hand for personal use but sets limits only for listed species; this one is not listed, so its status there is ambiguous: confirm with the park. Not on Prince William Forest Park’s list. Rock Creek Park (which also runs Glover-Archbold, Battery Kemble, the western and northern Civil War Defenses forts and many small DC reservations) bans gathering any fruit, nut, berry or seed. Pick on private land only with the owner’s permission. A major wildlife food plant.
- C&O Canal NHP (incl. Great Falls MD, trail-side only)
C&O 2026 compendium 2.1(c)(1): 'Edible fruits, nuts, berries, and mushrooms may be gathered by hand for personal use or consumption.' The limits table that follows does not list this species. 36 CFR 2.1(c)(1) requires designating 'certain' fruits, so the narrower reading (listed species only) is also possible. Confirm with the park.
- Virginia State Parks
4VAC5-30-50 bars gathering any plant without a permit, except that edible fruits, berries, fungi or nuts may be collected for personal or individual use; hackberry is an edible fruit
Where you may pick: what this means
For each park system: “yes” where its current rules (the park’s compendium or regulation) allow this plant or part, with the limit; “ambiguous” where the wording may or may not cover it, so ask the park; “no” where it is not allowed. Rock Creek Park, the GW Parkway sites (including Great Falls VA and Theodore Roosevelt Island), the National Mall, Montgomery and Prince George’s parks, Maryland state parks, and Fairfax and Arlington parks prohibit picking. Wolf Trap National Park for the Performing Arts allows blackberries and raspberries (one gallon per person per day) and chestnuts (one gallon per person per day). National Park Service rules are reissued every year; other parks change theirs from time to time, so check the park’s current rules. The Where you may pick page has every park’s rules.
Ways to use it
- eat raw as a trail nibble (thin, sweet, date-like flesh over a hard seed; Towson Glen Arboretum)
- jelly and preserves (NC State)
- traditional Native American use: the whole fruit, seed included, pounded into a storable food; also used dried as a seasoning (Wildflower Center)
Keeping
Fruit hangs on the tree into winter, so gather as needed and keep it dry and airtight for up to about a year.
- Use within
- months+
- Keeps fresh
- The fruit ripens in September and often stays on the tree through winter (NC State), drying in place, so pick as needed. Picked dry fruit keeps like other dried fruit, stored cool, dry and airtight.
- Keeping basis
- general guidance for its type
Ways to keep it
Dry as researched: dry/dehydrate; canning: n/a (not shelf-canned)
Traditionally used dried as a seasoning, or pounded whole (seed included) into cakes that could be stored (Wildflower Center). Store in airtight jars in a cool, dark place; dried fruit keeps about 1 year at 60°F or 6 months at 80°F (NCHFP).
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
How much of a day’s needs one standard serving (140 g) provides, using the FDA’s daily values and serving sizes. The FDA calls 20% or more “high” and 10–19% a “good source”. Every figure below is listed with its source; where the sources disagree, all of them are shown and no conclusion is drawn.
Calcium: high
Unconfirmed: only one analysis, and it would rank 1 of 105 raw fruits in USDA SR Legacy.
Wainio & Forbes 1941: whole fruit with its stone. Whole fruit ground with its stone, fresh basis, as when hackberries are pounded whole, seed included; most of the calcium and ash is probably in the stone (AI inference, not stated in the paper).
Wainio & Forbes 1941: 1051% of daily value
Sample: Celtis occidentalis (name as printed), field-collected in a forest wildlife-food survey (the paper does not say wild or planted; only three nut samples were bought at market), Centre County, Pennsylvania, collected Nov. 2, 1939; portion analyzed 'Whole berries' (whole fruit, stone ground in with the flesh); single sample; 21.4% moisture as collected
Recorded: 9.76 percent (g per 100 g) (fresh basis, whole fruit as collected (seeds ground in with the flesh), as printed). Working: 9760 mg per 100 g × 140 g ÷ 100 = 13664 mg; daily value 1300 mg; 1051%.
The chemical composition of forest fruits and nuts from Pennsylvania
Magnesium: high
Unconfirmed: only one analysis, and it would rank 1 of 103 raw fruits in USDA SR Legacy.
Wainio & Forbes 1941: 127% of daily value
Sample: Celtis occidentalis (name as printed), field-collected in a forest wildlife-food survey (the paper does not say wild or planted; only three nut samples were bought at market), Centre County, Pennsylvania, collected Nov. 2, 1939; portion analyzed 'Whole berries' (whole fruit, stone ground in with the flesh); single sample; 21.4% moisture as collected
Recorded: 0.38 percent (g per 100 g) (fresh basis, whole fruit as collected (seeds ground in with the flesh), as printed). Working: 380 mg per 100 g × 140 g ÷ 100 = 532 mg; daily value 420 mg; 127%.
The chemical composition of forest fruits and nuts from Pennsylvania
Phosphorus: good source
Unconfirmed: only one analysis, and it would rank 1 of 105 raw fruits in USDA SR Legacy.
Wainio & Forbes 1941: 19% of daily value
Sample: Celtis occidentalis (name as printed), field-collected in a forest wildlife-food survey (the paper does not say wild or planted; only three nut samples were bought at market), Centre County, Pennsylvania, collected Nov. 2, 1939; portion analyzed 'Whole berries' (whole fruit, stone ground in with the flesh); single sample; 21.4% moisture as collected
Recorded: 0.17 percent (g per 100 g) (fresh basis, whole fruit as collected (seeds ground in with the flesh), as printed). Working: 170 mg per 100 g × 140 g ÷ 100 = 238 mg; daily value 1250 mg; 19%.
The chemical composition of forest fruits and nuts from Pennsylvania
Figures left out, and why (1 study; 0 with no figure used)
The calendar counts a study with no figure used here when one of its vitamin, mineral or dietary fiber figures was left out as a dried sample, another part, or for an unclear species, part or basis; figures given per amount of juice are not counted.
- Wainio & Forbes 1941 (other figures from this study are used above): ash has no FDA daily value; crude fiber is a different measure from dietary fiber, the FDA daily value is for dietary fiber; no FDA daily value; protein: the FDA percent daily value for protein must be corrected for protein quality (PDCAAS, 21 CFR 101.9(c)(7)(ii)), which this analysis does not report; total fat has an FDA daily value, but the panels show only vitamins, minerals and dietary fiber
What was searched
- Europe PMC: searched 2026-10-09, 24 records; 24 after removing duplicates across databases; 0 candidates by title and abstract; 0 read in full; 0 with figures used
- PubMed: searched 2026-10-09, 12 records; 12 after removing duplicates across databases; 0 candidates by title and abstract; 0 read in full; 0 with figures used
- OpenAlex: searched 2026-10-09, 325 records; 237 after removing duplicates across databases; 2 candidates by title and abstract; 0 read in full; 0 with figures used
- Crossref: searched 2026-10-09, 74 records; 64 after removing duplicates across databases; 0 candidates by title and abstract; 0 read in full; 0 with figures used
- J-STAGE (Japan): searched 2026-10-09, 6 records; 6 after removing duplicates across databases; 0 candidates by title and abstract; 0 read in full; 0 with figures used
- USDA FoodData Central (online search): searched 2026-10-09, 0 records; 0 after removing duplicates across databases; 0 candidates by title and abstract; 0 read in full; 0 with figures used
- USDA FoodData Central (downloaded SR Legacy 2018 and Foundation 2026 tables): searched 2026-10-09, 0 records; 0 after removing duplicates across databases; 0 candidates by title and abstract; 0 read in full; 0 with figures used
- All databases together: 441 records from all databases, 303 unique, 2 candidates, 0 read, 0 used; 2 not read (paywalled 0, blocked automated access 2, not online 0)
- KCI (Korea), CNKI (China), SciELO (Latin America), CORE, USDA’s AGRICOLA and PubAg, Google Scholar, and national food composition tables other than USDA’s: not searched (October 2026).
The counts are of papers new in this search. Sources found before this search (such as USDA’s entries) were not counted again.
Each database was searched for the plant’s scientific and common names together with nutrient words (composition, nutrient, vitamin, mineral, fiber, protein and others), in titles and abstracts only. Papers that don’t name the plant there, and words not on the list (such as fat, energy and moisture), were missed unless another paper led to them; the AI researchers found some that way.
Found but not read (2)
- Nutritional Profiles of Plants Consumed by Military Macaw During the Breeding and Non-Breeding Seasons in the Alto Balsas Basin, Mexico authors not given 2025; not read: the site blocked automated access
- A Field Study of Winter Fruit Preferences of Cedar Waxwings McPherson JM 1987; not read: the site blocked automated access
Collected in October 2026 by AI research agents, following written rules; the calendar’s figures were then checked independently.
Native or not
- Origin
- native
- Native range
- central & eastern North America
- 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
- Common in the right habitat Estimate 784 = 289 research-grade iNaturalist sightings within 25 km + 459 needs-ID sightings counted at 97% (289 of the 298 research-grade Celtis sightings here are common hackberry) + 50 'cultivated' (planted) sightings (rule A); that is tier 2 by count (rule B). Final tier 2.
- Effort
- Grab & eat Pick and eat the thin, sweet flesh off the hard seed as a trail nibble; pounding whole fruit into a food 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
20 sources, each linked to the original.
- Prince William Forest Park Superintendent’s Compendium National Park Service, Prince William Forest ParkBacks up: picking rules
- C&O Canal NHP Superintendent’s Compendium National Park ServiceBacks up: picking rules
- Rock Creek Park Superintendent’s Compendium National Park ServiceBacks up: picking rules
- Celtis occidentalis (Common hackberry) Lady Bird Johnson Wildflower CenterBacks up: description, habitat, uses, keeping
- iNaturalist research-grade observations of Celtis occidentalis within 25 km of downtown DC iNaturalistBacks up: findability
- 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
- Celtis occidentalis (Common Hackberry) (Digital Atlas of the Virginia Flora) Virginia Botanical Associates (Digital Atlas of the Virginia Flora)Backs up: habitat
- Celtis laevigata (Sugarberry) (Digital Atlas of the Virginia Flora) Virginia Botanical Associates (Digital Atlas of the Virginia Flora)Backs up: habitat
- Packaging and Storing Dried Foods National Center for Home Food Preservation (Univ. of Georgia)Backs up: keeping
- USDA PLANTS Database: Celtis occidentalis (CEOC), native status USDA NRCSBacks up: native or invasive status
- Virginia Invasive Plant Species List (effective date: September 2024) Virginia Department of Conservation and Recreation, Division of Natural HeritageBacks up: native or invasive status
- 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
- 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
- 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
- Invasive Plants in the District DC Department of Energy & EnvironmentBacks up: native or invasive status
- Common Hackberry (Celtis occidentalis) Plant Fact Sheet USDA NRCS Plant Materials ProgramBacks up: season, description
- Silvics of North America: Hackberry USDA Forest ServiceBacks up: season, description
- Celtis occidentalis NC State Extension Plant ToolboxBacks up: season, description, uses, habitat, safety, keeping
- Wild Edibles of Missouri (Jan Phillips) Missouri Department of ConservationBacks up: season, uses, description
- Common Hackberry Towson University, Glen ArboretumBacks up: season, uses, habitat, description