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A Forager’s Year

No. 114

Water chestnut

Trapa natans (also two-horned T. bispinosa var. iinumai)

European water chestnut, water caltrop, two-horned trapa

Nut & seed nut kernel (boiled; from the spiny floating fruit)

Drawing: Britton & Brown, Illustrated Flora (1913)

Find
Patchy
Effort
Real work
ID risk
Beginner
Origin
non-native ★★★
Safety marks
  • Cook first
  • Spray risk
Uses
  • Baking & desserts
  • 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

Picking: The rules are unclear. Ask the park. 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.

Safety marks and flags

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.

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

An annual water plant rooted in the mud, with a floating rosette of leaves that have saw-tooth edges and an inflated leaf stalk that keeps them afloat (Plant Invaders of Mid-Atlantic Natural Areas). The fruit has a fleshy green, mottled outer skin that sloughs off to reveal a hard, black, nut-like seed 1–2 inches across, with four spines on Eurasian water chestnut and two on two-horned water chestnut (Plant Invaders of Mid-Atlantic Natural Areas). Eurasian water chestnut has white flowers and all-green leaves; two-horned water chestnut has pink flowers and leaves with red undersides (Virginia DWR). Inside the hard shell is a large, starchy seed leaf (Hummel & Kiviat review). Eat The Weeds describes the flavor as similar to tree chestnuts. It is not the Chinese water chestnut sold in cans, which is the corm of an unrelated sedge (USGS). Two-horned water chestnut was identified as Trapa bispinosa var. iinumai (Virginia DCR); Trapa bispinosa is the only domesticated water chestnut and a seasonal food in China, Japan, Taiwan and Vietnam (Ecology and Evolution, 2024).

Safety

Always cook the nuts. Raw nuts are unsafe: a review in the Journal of Aquatic Plant Management (Hummel & Kiviat) says raw nuts of the two-horned kind contain substances harmful to the digestive tract and must be boiled to be edible, and that the Asian custom of eating raw water chestnut spreads a giant intestinal fluke. CDC says improperly cooked water caltrops can pass that fluke to people; it is found in Asia and the Indian subcontinent (CDC). CDC also says people most often catch the Fasciola liver fluke by eating raw watercress or other freshwater plants. The plant takes up heavy metals: USGS notes cadmium, nickel and cobalt, and a study in India found alarming metal levels in the kernels of plants from polluted waters, which boiling reduced (Environmental Monitoring and Assessment, 2001). The same review says contaminant levels, pathogens and parasites in North American water chestnut fruits have not been studied and might limit their use for food. No toxic part is named in the sources checked (USGS; Virginia DCR; Plant Invaders of Mid-Atlantic Natural Areas). Two other floating plants are compared with water chestnut by their leaves, mosaic plant and creeping water primrose, and neither bears a horned nut (USGS; Virginia DCR). Mosaic plant is much smaller, with yellow flowers (USGS; Virginia DCR). The University of Nebraska says creeping water primrose’s berries may be mildly poisonous, while Washington’s noxious weed board says it is not known to be toxic. The nuts' sharp spines can pierce shoe soles (Maryland DNR), gloves (Virginia DCR) and bicycle tires (National Park Service), and barbed spine tips can break off in the skin and cause infection (Hummel & Kiviat review). Dense beds may have played a part in three drownings in the Hudson River (Hummel & Kiviat review), so take care wading or paddling among them. Infested ponds and rivers are sometimes treated with herbicides as part of control efforts (Maryland DNR).

Lookalikes

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
The black nut with two or four sharp horns is easy to recognize, and no toxic lookalike nut is named. Mosaic plant and creeping water primrose, which USGS and Virginia DCR compare with water chestnut by their floating leaves, bear no horned nut; creeping water primrose’s berries may be mildly poisonous (University of Nebraska).
Handling hazards
Thorns (moderate)
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 Jul
Peak
early Aug–late Sep
Ends
early Nov

Two-horned water chestnut, the kind mostly found around DC, may flower and fruit from June until frost (Virginia DWR; Virginia DCR). In New York, fruits mature from mid-July into September; ripe nuts drop from the plant and sink (Hummel & Kiviat review). In the Mid-Atlantic, flowering can run through November or until the first hard freeze, and the plants die back in late autumn (Plant Invaders of Mid-Atlantic Natural Areas; Virginia DCR). All dates are estimates: no DC-area source dates the ripe nuts, and only six iNaturalist sightings within 25 km of DC are marked as fruiting (July to October).

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: Virginia sources give fruiting from June but not when nuts are ripe; with about a month from flower to ripe fruit and mid-July maturity reported for New York, ripe nuts are estimated from mid July.

Peak

estimated: No source names a peak; early August to late September is the main maturing period given for New York, inside the July-to-October span USGS gives.

End

estimated: No source dates the last ripe nuts near DC; early November allows for fruit ripening on plants until frost kills them in late autumn, and the six DC-area fruiting records on iNaturalist end in October.

Evidence

start: Virginia DWR: 'Two-horned trapa may flower and fruit from June until frost.' Hummel & Kiviat (New York): 'The fruits mature from mid-July into September'. Eat The Weeds: 'Fruits ripen in about a month'. | peak: Hummel & Kiviat (New York): 'The fruits mature from mid-July into September'. USGS: 'flowers and fruits develop from July to October'. | end: Plant Invaders of Mid-Atlantic Natural Areas: 'Flowering occurs from June through November or until the first hard freeze.' Virginia DCR: 'two-horned trapa dies back in late autumn.' Virginia DWR: fruit 'from June until frost'.

Where to look

Still, sunny ponds and lakes, logged most at Greenbelt Lake in Buddy Attick Lake Park (City of Greenbelt; picking rules not checked) and Lake Accotink in Springfield (Fairfax County parks ban removing any plant part without written permission). The C&O Canal and Virginia state parks may or may not count its nut-like seeds as allowed nuts (ask the park first), and none is logged in Mason Neck or Leesylvania. Maryland bars transporting water chestnut, and Virginia bars moving two-horned trapa, without a permit.

Habitats
wetlands, marshes & pond edges
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

  • Buddy Attick Lake Park (City of Greenbelt)

    16 sightings · Legal to pick: unknown · see them on iNaturalist

    Picking rules not checked.

No picking here (1 place)
  • Lake Accotink Park

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

    Look but don’t pick: Fairfax County parks ban removing any plant part without written permission.

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

  • boiled: boil the nuts, then crack the hard shell and eat the starchy kernel; raw nuts must be boiled to be edible (Hummel & Kiviat review)
  • roasted or fried kernels (Eat The Weeds)
  • preserved in honey and sugar, or candied (Eat The Weeds)
  • flour: dried kernels ground into flour for bread and other foods (Hummel & Kiviat review; Eat The Weeds)

Keeping

Boil before eating; to keep them, dry the kernels soon after gathering and store dried, shelled kernels in the refrigerator or freezer.

Use within
within a few days
Keeps fresh
No source gives a keeping time for fresh water chestnuts, which have a high moisture content (Hummel & Kiviat review). Drying of nuts and seeds should begin soon after harvest, usually within 24 hours, and dried, shelled nuts must be refrigerated or frozen (general guidance for nuts and seeds, WSU).
Keeping basis
general guidance for its type

Ways to keep it

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

    Dried water chestnuts were ground into flour and used to make various foods (Hummel & Kiviat review). Dry at 90 to 100°F in a single layer, and keep dried, shelled nuts refrigerated or frozen (general guidance for nuts and seeds, WSU).

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

Two-horned water chestnut (Trapa bispinosa var. iinumai), first found in the U.S. at Pohick Bay in 2014, makes up most DC-area sightings; iNaturalist treats it as a variety of Trapa natans.

Origin
non-native
Native range
Europe, Asia and Africa (Eurasian water chestnut); Taiwan, China, Korea and Japan (two-horned water chestnut)
Invader credit
★★★
Virginia invasive rank
High
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 63 = 62 research-grade iNaturalist sightings within 25 km + 1 'cultivated' (planted) sighting (rule A); that is tier 3 by count (rule B). Rule D does not apply: USGS says Eurasian water chestnut was "Eradicated from the Potomac River in the District of Columbia and Virginia", but that four-horned plant makes up at most 3 of the 62 research-grade sightings here (59 are two-horned trapa), and Virginia DCR says two-horned trapa "is known to occur at over 200 locations in northern Virginia"; Maryland DNR’s older note that "so far there have been no infestations discovered on Maryland’s side of the river" is about the river only, and the same page reports two-horned trapa in Greenbelt Lake and at Beltsville; the Smithsonian checklist’s "All four DC specimens very old" describes herbarium records, not a present-day scarcity. Final tier 3.
Effort
Real work Pick the nuts from the floating plants, boil them thoroughly, then crack the hard, spiny shell and pick out the starchy kernel; drying and grinding kernels for flour is more work.
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

31 sources, each linked to the original.

  1. 2VAC5-317 Regulations for the Enforcement of the Noxious Weeds Law (full chapter) Virginia Law Library (law.lis.virginia.gov)Backs up: picking rules
  2. C&O Canal NHP Superintendent’s Compendium National Park ServiceBacks up: picking rules
  3. Prince William Forest Park Superintendent’s Compendium National Park Service, Prince William Forest ParkBacks up: picking rules
  4. Rock Creek Park Superintendent’s Compendium National Park ServiceBacks up: picking rules
  5. 4VAC5-30-50. Flowers, plants, minerals, etc. Virginia Law Library (law.lis.virginia.gov)Backs up: picking rules
  6. COMAR 08.02.19.04 Classification of Nonnative Aquatic Organisms Maryland Division of State Documents (Code of Maryland Regulations)Backs up: picking rules, native or invasive status
  7. Origin of domesticated water chestnuts (Trapa bispinosa Roxb.) and genetic variation in wild water chestnuts (Ecology and Evolution, 2024) PubMed Central (NIH/NLM)Backs up: description
  8. Trapa natans (water chestnut): Nonindigenous Aquatic Species fact sheet U.S. Geological SurveyBacks up: description, habitat, safety, season, native or invasive status
  9. Invasive Plant Alert: Two-horned Trapa, Two-horned Water Chestnut (Trapa bispinosa var. iinumai) Virginia Department of Conservation and Recreation, Division of Natural HeritageBacks up: description, habitat, season, safety, picking rules
  10. Two-Horned Water Chestnut Virginia Department of Wildlife ResourcesBacks up: description, season
  11. Plant Invaders of Mid-Atlantic Natural Areas, Field Guide (Swearingen & Fulton, 2022): Water chestnut, pp. 34-35 Mid-Atlantic Invasive Plant Council / Passiflora Press (hosted by Bugwood/Mid-Atlantic Invaders Tool)Backs up: description, season, safety, picking rules, native or invasive status
  12. Water Chestnut, Water Caltrop Eat The Weeds (Green Deane)Backs up: description, uses, habitat, season
  13. iNaturalist research-grade observations of Trapa natans (incl. var. bispinosa) within 25 km of downtown DC iNaturalistBacks up: findability
  14. 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
  15. Two-Horned Trapa (Trapa bispinosa) National Park ServiceBacks up: habitat, safety
  16. Aquatic Invasive Species: Water Chestnut Maryland Department of Natural ResourcesBacks up: habitat, safety, picking rules
  17. Trapa bispinosa var. iinumai (water chestnut): Nonindigenous Aquatic Species fact sheet U.S. Geological SurveyBacks up: habitat, safety, native or invasive status
  18. USDA PLANTS Database: Trapa natans (TRNA), native status USDA NRCSBacks up: native or invasive status
  19. Virginia Invasive Plant Species List (effective date: September 2024) Virginia Department of Conservation and Recreation, Division of Natural HeritageBacks up: native or invasive status
  20. 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
  21. 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
  22. Invasive Plants in the District DC Department of Energy & EnvironmentBacks up: native or invasive status
  23. Public Health Image Library, image 26712: water caltrops (Trapa) Centers for Disease Control and PreventionBacks up: safety
  24. DPDx: Fasciolopsiasis Centers for Disease Control and PreventionBacks up: safety
  25. Distribution of metals in aquatic edible plants: Trapa natans and Ipomoea aquatica (Rai & Sinha, Environmental Monitoring and Assessment, 2001), abstract Aprifel (abstract reproduced from PubMed)Backs up: safety
  26. Water Chestnut (Trapa natans) Maryland Biodiversity ProjectBacks up: safety details
  27. Review of World Literature on Water Chestnut with Implications for Management in North America (Journal of Aquatic Plant Management 42:17-28, 2004; Hummel & Kiviat) Aquatic Plant Management Society (peer-reviewed journal)Backs up: safety, uses, description, season, storage, keeping
  28. About Liver Flukes Centers for Disease Control and PreventionBacks up: safety, safety details
  29. Creeping Water Primrose University of Nebraska-Lincoln, Nebraska Cooperative Fish and Wildlife Research UnitBacks up: safety, safety details
  30. Floating Primrose-Willow (Ludwigia peploides) Washington State Noxious Weed Control BoardBacks up: safety, safety details
  31. Food Safety and Preservation: Nuts & Seeds Washington State University Extension, Lewis CountyBacks up: storage, keeping