The Caddo false foxglove. The pale bugseed. The largeleaf leather-root.
These are just a few of the plant species and varieties that have gone extinct in the continental United States and Canada since the beginning of European colonization.
A new paper documents 65 such plant extinctions — five small trees, eight shrubs, 37 perennial herbs and 15 annual herbs — the losses of most of which have never been reported before. Most of these species had limited ranges or were known from single sites, and likely went extinct following the destruction of their habitats. A few were lost due to dams, invasive species or overgrazing.
This new record of what we’ve lost contains 51 species and 14 varieties. These variants, or “infraspecific taxa,” as the paper calls them, may not have been full species, but they still contained unique and potentially important genetic traits.
The list includes a three-foot-tall daisy called Marshallia grandiflora, which some of the same authors declared extinct earlier this year.
It also includes seven plants that are now considered “extinct in the wild,” meaning they only exist in botanical gardens. Four of those “extinct in the wild” plants were, until this paper, thought to still be living in the wild. The evidence now suggests that three trees from the hawthorn family — Crataegus delawarensis, C. fecunda and C. lanuginose — and a bittersweet shrub variety called Euonymus atropurpureus var. cheatumii have narrowly avoided extinction due to their cultivation in botanical gardens.
“I was astonished,” says biologist Wesley Knapp of the North Carolina Natural Heritage Program, the lead author of the new paper. “The fact that botanical gardens had the last known living material of a species, yet they were unaware of this, was shocking and it’s spurring future work. Unfortunately for some species, there is little hope aside from a future in gardens or seedbanks. This is certainly better than extinction.”
Losing 65 species and varieties is bad enough, but, as the paper also warns, the continent has probably experienced a much higher level of extinction than could ever be catalogued or assessed. That’s because Europeans settlers typically moved into new areas, particularly the American West, before scientists could document the species that lived there. If those species had small ranges, the authors write, they could have easily disappeared due to agriculture and other development before they were identified or named by scientists.
Of the extinctions that researchers could catalog, 19 came from California, nine from Texas and five from New England. Only one extinct plant on the list came from Canada — suggesting more of a knowledge gap or a research opportunity than necessarily a better conservation record. “It is highly unlikely that New England would have seen five extinctions but adjacent parts of Canada zero. I suspect this is all an artifact of our knowledge — or lack of,” says Knapp.
As bad as this news is, the authors caution that most of these losses should be considered “presumed extinctions.” Even though many species have not been seen for decades, they could reemerge if people look long and hard enough.
“Surprises happen,” says Knapp. He points to this year’s rediscovery of a grass subspecies called Sphenopholis interrupta californica — which was found in California after previously being known from two sites in Mexico — and the famous case of the Wollemi pine (Wollemia nobilis), which was known only from fossil records before it was found alive in Australia in 1995.
“Even plants not seen for millions of years, or plants completely new to a geographic area where they have not been seen before, can be found,” he says. “I hope every plant on this list is ultimately rediscovered. Drawing attention to them is the best way to possibly help spur their rediscovery.”
And the paper may serve as incentive to find and save other plant species, especially ones that have been sparsely documented in the scientific literature, or species without known living specimens available for genetic testing.
To assist in these types of efforts, the authors developed what they call the “Index of Taxonomic Uncertainty,” a new methodology that ranks species based on how often they’ve been studied. The rarer the study, the lower the level of certainty about whether the plants truly represent species, subspecies or variants, or if even if they still exist. The paper’s supplements contain rankings on more than 400 such plants, about 150 of which have rarely been seen or never catalogued after their initial scientific description.
Knapp says this system, or others like it, may help to reassess rarely seen species or inspire efforts to fill scientific gaps about little-known plants. “Our knowledge is ever-changing,” he says.
That’s reflected in the paper itself, which in earlier drafts projected 53 species extinctions, not the published 51. One of the species was moved to the variety list during peer review, Knapp says.
As to the other? Well, Knapp says recent reports suggest an assumed-lost species of hollyhock could represent another possible rediscovery — proof that hope remains and that we should never give up looking for species we may have lost.
The full list of extinct plant species appears below:
| Taxonomic name | Common name (if known) |
| Agalinis caddoensis | Caddo false foxglove |
| Arctostaphylos franciscana | Franciscan manzanita |
| Astilbe crenatiloba | Roan Mountain false goat’s beard |
| Astragalus endopterus | Sandbar milkvetch |
| Astragalus kentrophyta var. douglasii | Barneby Douglas’ thistle milkvetch |
| Astragalus robbinsii var. robbinsii | Robbins’ milkvetch |
| Atriplex tularensis | Bakersfield smallscale, Tulare saltbush or Tulare orach |
| Blephilia hirsuta var. glabrata | Hairy wood-mint |
| Boechera fructicosa | |
| Brickellia chenopodina | Chenopod brickellbush |
| Brickellia hinckleyi Standley var. terlinguensis | |
| Calochortus indecorus | Sexton Mountain mariposa lily |
| Calochortus monanthus | Single-flowered mariposa lily or Shasta River mariposa lily |
| Calystegia sepium binghamiae | Bingham’s false bindweed |
| Castilleja leschkeana | Point Reyes paintbrush |
| Castilleja uliginosa | Pitkin Marsh Indian paintbrush |
| Cirsium praeteriens | Palo Alto thistle |
| Corispermum pallidum | Mosyakin pale bugseed |
| Crataegus austromontana | Valley Head hawthorn |
| Crataegus delawarensis | |
| Crataegus fecunda | St. Clair or fecund hawthorn |
| Crataegus lanuginose | Woolly hawthorn |
| Cryptantha aperta | Grand Junction cryptantha |
| Cryptantha hooveri | Hoover’s cryptantha |
| Cryptantha insolita | Las Vegas cryptantha |
| Dalea sabinalis | Sabinal prairie clover |
| Digitaria filiformis var. laeviglumis | Slender crabgrass |
| Diplacus traskiae | Mimulus traskiae |
| Eleocharis brachycarpa | Shortfruit spikerush |
| Elodea schweinitzii | Schwe initz’s waterweed |
| Erigeron mariposanus | Foothill fleabane, Mariposa daisy or Mariposa erigeron |
| Eriochloa michauxii var. simpsonii | Simpson’s cupgrass |
| Euonymus atropurpureus var. cheatumii (extinct in the wild) | Eastern wahoo |
| Franklinia alatamaha | Franklin tree |
| Govenia floridana | Gowen’s orchid |
| Hedeoma pilosa | Old blue false pennyroyal |
| Helianthus nuttallii parishii | Los Angeles sunflower or Parish’s sunflower |
| Helianthus praetermissus | Lost sunflower |
| Isocoma humilis | Zion goldenbush or Zion jimmyweed |
| Juncus pervetus | Blunt-flower rush |
| Lechea lakelae | Lakela’s pinweed |
| Lycium verrucosum | San Nicholas desert thorn or San Nicolas island desert thorn |
| Marshallia grandiflora | Barbara’s buttons |
| Micranthemum micranthemoides | Pearl weed |
| Monardella leucocephala | |
| Monardella pringlei | Pringle’s monardella |
| Narthecium montanum | Appalachian yellow asphodel |
| Orbexilum macrophyllum | Largeleaf leather-root |
| Orbexilum stipulatum | Largestipule leather-root or Falls-of-the-Ohio scurfpea |
| Paronychia maccartii | McCart’s nailwort |
| Plagiobothrys lamprocarpus | Shiny-fruited allocarya |
| Plagiobothrys lithocaryus | Mayacamas popcorn flower |
| Plagiobothrys mollis var. vestitus | Petaluma popcorn flower |
| Polygonatum biflorum var. melleum | Smooth Solomon’s seal |
| Potentilla multijuga | Ballona or lost cinquefoil |
| Potentilla uliginosa | Cunningham marsh cinquefoil |
| Proboscidea spicata | New Mexico unicorn-plant |
| Prunus maritima var. gravesii | |
| Quercus tardifolia | Chisos Mountains oak or lateleaf oak |
| Ribes divaricatum var. parishii | Straggly gooseberry |
| Rumex tomentellus | Mogollon dock |
| Sesuvium trianthemoides | Texas sea-purslane |
| Sphaeralcea procera | Porter’s globe mallow |
| Tephrosia angustissima var. angustissima | Coral hoary pea |
| Thismia americana | Thismia or banded Trinity |
