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The Vascular Plants Technical Committee dates to the organization of the Survey in 1979, and produced "Chapter 1 - Plants" for the 1985 Species of Special Concern in Pennsylvania publication. Its membership includes botanists from colleges and universities, natural history museums, conservation organizations and state and federal agencies. Following the passage of P.L. 597, No. 170 - The Wild Resource Conservation Act, and during the development of the implementing regulations, Title 25, Chapter 82 - Conservation of Pennsylvania Native Wild Plants, the VPTC has provided scientific input to DER Bureau of Forestry. An annual review session has been held each year to recommend additions to or changes in the status of plants classified as extirpated, endangered, threatened, or rare under the regulations. In addition, other policy matters affecting enforcement of the regulations has been addressed. The Vascular Plants Technical Committee also provides an important forum for exchange of information among botanists working in the state.

Red Trillium
photograph courtesy of Merlin Benner

The Vascular Plants Technical Committee members are:

Pennsylvania Vascular Plants


Sue A. Thompson
Carnegie Museum of Natural History


Pennsylvania has a diverse vascular flora coupled with a long history of botanical work within the state dating from the 18th century. A variety of habitats and the occurrence of several physiographic provinces contribute to Pennsylvania's floristic diversity. Habitats range from freshwater tidal marshes to limestone barrens, and northern and southern forest types both occur within the state.

Seminal works on vascular plants in Pennsylvania include the Flora of Pennsylvania (Porter 1903), Wild Flowers of Western Pennsylvania and the Upper Ohio Basin (Jennings and Avinoff 1953), and Atlas of the Flora of Pennsylvania (Wherry et al. 1979). Given the age of Porter's work and the fact that Jennings and Avinoff's publication included only western Pennsylvania, the major reference work on the flora of the state was, until recently, the atlas by Wherry et al. (1979).

Initiated in the 1930s and based on over 250,000 herbarium specimens, this atlas claimed to be complete, stating ". . .when a particular species is not shown on our distribution maps, it may be reasonably supposed that it does not occur there. . ." (Wherry et al. 1979:vii). However, many years elapsed between the start of this project and publication of the atlas in 1979, and during this period thousands of additional specimens documenting new distributions of Pennsylvania plants were collected (e.g., Thompson et al. 1989).

Much of this new distributional data was incorporated into a revised atlas, The Vascular Flora of Pennsylvania: Annotated Checklist and Atlas published in 1993 (Rhoads and Klein 1993), which also incorporated taxonomic and nomenclatural changes since the 1979 atlas. This "new atlas" maps 3,318 taxa of vascular plants in Pennsylvania, including both introduced and native species, and is now the major reference on the Pennsylvania flora.

Although published in 1993, the new atlas is already out-of-date. Since its publication, more than 20 species have been added as new to Pennsylvania, including both native and exotic plants, and many new distribution records within the state have been reported (e.g., Cusick and Thompson 1994, Isaac and Isaac 1997, Naczi and Thieret 1996). The vascular plant flora of Pennsylvania is dynamic and always changing, and thus both inventory and monitoring of the state's flora must be on going.


Native plants comprise slightly less than 63% of the vascular flora of Pennsylvania. Of these native taxa, approximately 30% are currently listed as plants of special concern (Fig. 1). More than 5% (116) of native plant species are believed to be extirpated in Pennsylvania, and an additional 20% are classified as Endangered (288), Threatened (80), rare (52), or vulnerable (3) (Appendix 1). Another 93 species are currently classified as undetermined, pending assignment to a specific status. The figure of 30% does not include the approximately 135 species which were under review as of July 1997 by the Vascular Plant Technical Committee for listing as species of special concern.

Thirty-seven Pennsylvania plant species are listed as Globally Rare (G3 rank), Threatened (G2 rank), or Endangered (G1 rank) (Pennsylvania Natural Diversity Inventory (PNDI). Two species which occurred in Pennsylvania, Schweinitz's waterweed (Elodea schweinitzii) and Nuttall's mud-flower (Micranthemum micranthemoides), are considered to be extinct throughout their ranges (Rhoads and Klein 1993).

Status of vascular plants native to Pennsylvania
Fig. 1 Status of vascular plants native to Pennsylvania.

The high number of Pennsylvania Endangered and Threatened plants may be attributable to the geographic position of Pennsylvania straddling a number of physiographic regions and the diversity of habitats found in the state. Seventy-seven percent of Endangered and Threatened plants in Pennsylvania are at the edge of their geographic range (Walck 1996). Although water-dependent habitats occupy only about 2% of the land surface in Pennsylvania, 57% of Endangered and Threatened plant species grow in these habitats (Walck 1996). Not surprisingly, families with the largest number of Pennsylvania Endangered and Threatened plants, the sedges (Cyperaceae), grasses (Poaceae), and composites (Asteraceae), are the families with the greatest number of species in Pennsylvania.


More than any other group of organisms in Pennsylvania, the state's native flora has been impacted by the establishment of alien species. Over 37% of the vascular plant species now growing within the borders of Pennsylvania are not native. This figure is much higher in some groups, such as the mustard family (Brassicaceae), for which almost 80% of the species in Pennsylvania are introduced.

Exotic species range from noxious weeds (Appendix 2), such as purple loosestrife (Lythrum salicaria) and mile-a-minute weed (Polygonum perfoliatum), to plants that many people enjoy as Pennsylvania wildflowers, such as ox-eye daisy (Chrysanthemum leucanthemum) and even a species of orchid (Epipactis helleborine). Exotic plant

Species are a significant threat to the native flora and are discussed in that context below.


Threats to the vascular flora of Pennsylvania are of 2 kinds: those threats that directly affect plants and their habitats and threats that impede study of the flora. Historically, the greatest threats to the native Pennsylvania flora have been land use practices that alter natural habitats, including deforestation, urban and suburban expansion, road-building through natural habitats, and draining of wetlands.

Colonization of disturbed areas and native habitats by invasive, introduced species such as garlic mustard (Alliaria petiolata) and multiflora rose (Rosa multiflora) is an increasing threat. Introduced pests and diseases, including the gypsy moth (Lymantria dispar) and Dutch elm disease, have altered the composition of many forests in Pennsylvania, especially those already weakened by other threats, such as white-tailed deer (Odocoileus virginianus). Over-browsing by white-tailed deer has resulted in a decrease in species diversity, changes in forest structure in many parts of Pennsylvania, and a threat to more than 20 species of Endangered and Threatened wildflowers (Rhoads 1996). Public education about the benefits of biodiversity is key to campaigns to ameliorate many of these direct threats. As more and more people enjoy Pennsylvania's natural resources, recreational use is also negatively impacting native habitats.

In addition to direct threats, native plant species are threatened by the lack of expertise and resources to address issues important to their preservation. There is a critical shortage of trained plant systematists and their support personnel not only in Pennsylvania, but worldwide. A recent survey found only 940 systematic biologists (including botanists and zoologists) employed by Ph.D.-granting universities in the entire United States (Anonymous 1994). Currently no Pennsylvania university maintains a recognized doctorate program in plant systematics. Efforts are under way at both the national and state level to develop programs to recruit, educate, and train systematists and other biodiversity specialists, but meaningful post-graduate employment may still remain a problem.

The lack of employment opportunities for trained systematists stems in part from a lack of infrastructure support for collections-based resources and the types of field projects they conduct. Appropriate scientific infrastructure is necessary to effective data gathering that results in informed decision making. Like elsewhere in the world, Pennsylvania suffers from a lack of adequate funds dedicated to these issues.

Integrated studies of the flora of Pennsylvania are hampered by the historic division of plant studies among major herbaria in the eastern, western, and central regions, and the lack of coordination among conservation organizations. This poor statewide coordination between and among regions, state agencies, and private institutions is improving, but still hinders comprehensive and integrated studies of the state's flora.


For the past several years, the vascular plant technical committee of the Pennsylvania Biological Survey has concentrated on developing and refining a checklist of plant species of special concern in Pennsylvania and assigning an appropriate status to each species. Further refinement of this list is on going, including a systematic assessment of all Pennsylvania native plant species to determine if any candidate species have been overlooked. This project resulted in approximately 135 additional species targeted for review as species of special concern.

Discovery of new localities and monitoring of known populations of special concern species is on going and involves staff of Pennsylvania Natural Diversity Inventory, the Western Pennsylvania Conservancy, and The Nature Conservancy, as well as botanists at many other institutions throughout the state. Staff at the Carnegie Museum of Natural History herbarium have targeted under-collected areas of the state for more intensive fieldwork on all vascular plants, not just species of special concern.

The Pennsylvania Flora Project, based at Morris Arboretum in Philadelphia, has been particularly active in recent years with the publication of the new atlas (Rhoads and Klein 1993) and plans to produce a field manual to the vascular flora of Pennsylvania by the end of the millennium (Rhoads and Block 1997; A. F. Rhoads, pers. comm.). In conjunction with the Academy of Natural Sciences in Philadelphia, they sponsor an annual Pennsylvania Flora Intern, housed at the Academy, and have already employed several students in this position.

Educational projects, including the development of materials on native wild plants, are under way by the Carnegie Museum of Natural History botany and education staffs. Preparation of information on potentially invasive species and on the use of native plants for landscaping is under way at the Bureau of Forestry.


Many of the vascular plants of selected areas of Pennsylvania have been extensively documented with probably over 400,000 herbarium specimens (including duplicates) currently available (Thorne et al. 1995). Most of these specimens are housed in herbaria at 3 Pennsylvania institutions (codes follow Holmgren et al. 1990): (1) the Academy of Natural Sciences, Philadelphia (PH) (including the herbarium of the University of Pennsylvania (PENN) which is housed at PH); (2) the Carnegie Museum of Natural History, Pittsburgh (CM); and (3) The Pennsylvania State University, University Park (PAC). The CM herbarium alone housed over 135,000 specimens of vascular plants collected in Pennsylvania as of July 1997.

In addition to the above 3 major repositories for Pennsylvania plant specimens, 16 other herbaria with vascular plants, associated mostly with colleges and universities, are located in Pennsylvania (Holmgren et al. 1990). Not all specimens of Pennsylvania plants are in Pennsylvania institutions, and important collections of especially older material are deposited at places such as the Field Museum (F) in Chicago; Gray Herbarium (GH) at Harvard University; New York Botanical Garden (NY) Bronx; and the US National Herbarium (US), Washington, D.C. Smaller collections at institutions in states bordering Pennsylvania (e.g., Youngstown State University (YUO) in Ohio and others) contain significant collections of Pennsylvania vascular plants.

While many of the specimens of Pennsylvania vascular plants represent historical collections, new material is continually being prepared and added to herbaria, especially those in Pennsylvania. For example, by July 1997 the CM herbarium had added almost 20,000 specimens collected in Pennsylvania since publication of the revised atlas.

The major primary database of Pennsylvania vascular plants is the CM herbarium database, which contains label data for all Pennsylvania specimens at CM. Data from new specimens are continually added and specimen data records are updated with changes in identification or nomenclature. Secondary databases (e.g., those which do not have a direct continuing link to the specimens on which data records are based) on Pennsylvania vascular plants include the Pennsylvania Flora database at Morris Arboretum, which contains records for all taxa occurring in Pennsylvania, and the Pennsylvania Natural Diversity Inventory database, which focuses on plant species of special conservation concern and contains records based on field surveys in addition to specimen-based records.

Knowledge of the vascular plants of Pennsylvania is adequate, and even relatively good for some taxa and areas of the state, at the basic floristic level. However, beyond alpha-level checklists, distribution maps, and some notions of which species are of special conservation interest, little is known about the plants of Pennsylvania. Species-specific issues such as genetic diversity, variation, ecology, habitat requirements, life history, or management needs remain unknown for the majority of vascular plants in Pennsylvania. Even in terms of basic floristics, there are still major gaps in our knowledge, which fall into 3 general categories: (1) spatial, (2) taxonomic, and (3) temporal.

Spatial: The long history of botanical fieldwork in Pennsylvania has resulted in a large number of specimens, which gives the impression that the state has been well collected. Unfortunately, this is not the case. A comprehensive field survey which systematically documented plants throughout the state has never been conducted. Staff at the 3 major herbaria tended to collect specimens near their institutions, and early botanists did not venture much into areas considered to be within the "territory" of the other institutions (W.E. Buker, pers. commun.). The CM herbarium, for example, has over 14,000 specimens from Allegheny County, where it is located, but just slightly more than 100 specimens from Columbia County in northeastern Pennsylvania. Until recent years, documentation of the Pennsylvania flora has been primarily on an ad hoc basis, and to this day significant areas of Pennsylvania remain botanical terra incognita.

Areas of the state that are poorly represented by botanical collections include the northern tier of counties, the extreme southwestern corner, counties along the southern border, regions that are remote from roads, and miscellaneous other areas throughout the state. In only 7 days of fieldwork in June 1990 and June 1994, botanists documented 80 species (in 29 genera) new to Bradford County, including 2 species also new to the state (Naczi and Thieret 1996). Another species new to Pennsylvania (Myosotis macrosperma) was collected several times since 1995 in 3 different counties along Pennsylvania's southern border, and the death-camas lily (Zigadenus elegans var. glaucus) was discovered in a relatively inaccessible area of Huntingdon County in 1994 (Isaac and Isaac 1997).

Taxonomic: The problem of taxonomically unresolved and difficult groups of plants is not unique to Pennsylvania. The status in Pennsylvania of notoriously difficult genera, such as Rubus (blackberries, raspberries, and dewberries), Crataegus (hawthorns), and Panicum (panic-grass), is a continuing problem, which will not be resolved by studies restricted to only Pennsylvania specimens. Resolution of the number of species of such genera in Pennsylvania must await taxonomic revisions of these groups.

The problem of taxonomic difficulties extends as well to proper curation of the hundreds of thousands of Pennsylvania specimens already in herbaria and the lack of botanical expertise to undertake this task. Often, "new" discoveries have been made based on herbarium specimens, which had been (1) overlooked, (2) not well curated, or (3) not correctly identified. In 1994, for example, 2 plant species were reported as "new" to Pennsylvania based on specimens collected by John Miller in the early 1900s and maintained by the Erie Historical Society and Planetarium until 1988 when they were donated to CM (Cusick and Thompson 1994). Another species reported for the first time in Pennsylvania in that same paper (Cusick and Thompson 1994) was a result of specimens which had been misidentified and were redetermined by the taxonomic expert in that group of plants.

Taxonomic problems and issues affect information on Pennsylvania vascular plants at all levels. In addition to supporting increased funding for taxonomic research and educational initiatives, increased curatorial attention to the many specimens already in hand is necessary.

Temporal: The atlas by Rhoads and Klein (1993) maps plant distributions in Pennsylvania based on specimens collected over many years, but it does not give any indication of year in which the specimens documenting the distribution maps were collected. For many species, this results in misleading distribution maps of current occurrences. Although the overall historical distribution may be known, the present distribution of the vascular plants of Pennsylvania, outside of a handful of Rare and Endangered species, remains unknown. The small-headed sunflower (Helianthus microcephalus) is presented in the 1993 atlas as occurring in 16 counties, based on over 68 specimens (Fig. 2). Of those specimens, however, only 4 were collected after 1969, the most recent one in 1987! Similarly, over 61% of the known Pennsylvania specimens of fire pink (Silene virginica), a showy plant that would attract botanists' attention, were collected prior to 1950.

Clearly there are major gaps in current knowledge on the distribution of vascular plant species in Pennsylvania. Plant inventory may be mostly complete, but  

Distribution of small-headed sunflowers
Fig 2. Distribution of small-headed sunflower (Helianthus microcephalus)
in Pennsylvania based on all specimens (upper map) versus distribution
of that same species based only on specimens collected after 1969 (lower map).

monitoring is needed to provide current information on most of the plant species in Pennsylvania. The inability to adequately monitor the state's flora can be attributed at least in part to lack of sufficient botanical expertise within the state and a decline in fieldwork focused on Pennsylvania. Until recently, the CM herbarium showed a dramatic decrease from the 1950s through the 1980s in the number of Pennsylvania plant specimens added to the collection (Fig. 3). Systematic field surveys of all areas and taxa are needed to address this problem.

In addition to lack of information on current plant distribution in Pennsylvania, there may also be problems associated with uneven data on a phenological basis. Collections of plant specimens are concentrated in the months from June to September with marked decreases in the number of specimens collected in early spring and late fall (CM Pennsylvania Plant Database). The occurrence and distribution of species with phenologies restricted to early spring and late fall may be skewed, and additional fieldwork is needed during early spring and late fall.

Number of Pennsylvania plant speciments in the Carnegie Museum of Natural History herbarium by year of collection
Fig. 3. Number of Pennsylvania plant specimens in the Carnegie Museum of
Natural History herbarium by year of collection.


I thank the many botanists from throughout the state who responded to my request for input on the status of our knowledge of Pennsylvania vascular plants. Funding from the Wild Resource Conservation Fund has been essential to many projects on vascular plants in Pennsylvania, especially those targeted as species of special concern.


Anonymous. 1994. Systematics agenda 2000: charting the biosphere, Technical Report. Systematics Agenda 2000, [New York].

Cusick, A. W., and S. A. Thompson. 1994. Noteworthy collections from Pennsylvania. Bartonia 58:69-73.

Holmgren, P. K., N. H. Holmgren, and L. C. Barnett. 1990. Index herbariorum. Part I: The herbaria of the world, Eighth ed. Regnum Vegetabile 120:1-693.

Isaac, B. L., and J. A. Isaac. 1997. Noteworthy collections: Pennsylvania. Castanea 62:131-132.

Jennings, O. E., and A. Avinoff. 1953. Wild flowers of western Pennsylvania and the Upper Ohio Basin. Univ. Pittsburgh Press, Pittsburgh, Pa. 2 vols.

Naczi, R. F. C., and J. W. Thieret. 1996. Additions to the flora of Bradford County, Pennsylvania. Bartonia 59:81-85.

Porter, T. C. 1903. Flora of Pennsylvania. Ginn and Co., Boston.

Rhoads, A. F. 1996. Something is missing. Pennsylvania Game News 16:10-13.

Rhoads, A. F., and T. A. Block. 1997. The Pennsylvania flora project: history and ongoing work of the Botany Department at the Morris Arboretum [abstract]. Am. J. Botany, Supplement 84:253.

Rhoads, A. F., and W. M. Klein, Jr. 1993. The vascular flora of Pennsylvania: annotated checklist and atlas. American Philosophical Society, Philadelphia, Pa. 636pp.

Thompson, S. A., W. E. Buker, and M. Macdonald. 1989. Notes on the distribution of Pennsylvania plants based on specimens in the Carnegie Museum of Natural History herbarium. Carnegie Mus. Nat. Hist. Spec. Publ. 14:1-55.

Thorne, S. G., K. C. Kim, K. C. Steiner (project co-directors), and B. J. McGuinness (ed.). 1995. A heritage for the 21st century: conserving Pennsylvania's native biological diversity. Pennsylvania Fish & Boat Comm., Harrisburg, Pa. 72pp.

Walck, J. L. 1996. Distribution, life forms, taxonomic categories, and habitats of the Endangered and Threatened vascular plants in Pennsylvania: A summary. Bartonia 59:49-54.

Wherry, E. T., J. M. Fogg, Jr., and H. A. Wahl. 1979. Atlas of the flora of Pennsylvania. Univ. Pennsylvania, Morris Arboretum, Philadelphia.

Appendix 1
Vulnerable, Rare, Threatened, Endangered, and Extirpated Vascular Plants of Pennsylvania as Listed by the Pennsylvania Biological Survey (March 1997).

Legislative Authority: Title 25 Chapter 82, Conservation of Pennsylvania Native Wild Plants, effective January 1, 1988; amended June 18, 1993.

Responsible Agency: Department of Conservation and Natural Resources.

Pennsylvania Vulnerable - Plant species which are in danger of population decline within this Commonwealth because of their beauty, economic value, use as a cultivar, or other factors which indicate that persons may seek to remove these species from their native habitats.

Pennsylvania Rare - Plant species which are uncommon within this Commonwealth because they may be found in restricted geographic areas or in low numbers throughout this Commonwealth.

Pennsylvania Threatened - Plant species which may become Endangered throughout most or all of their natural range within this Commonwealth, if critical habitat is not maintained to prevent their further decline in this Commonwealth, or if the species is greatly exploited by man.

Pennsylvania Endangered - Plant species which are in danger of extinction throughout most or all of their natural range within this Commonwealth, if critical habitat is not maintained or if the species is greatly exploited by man. This classification also includes populations of plant species that have been classified as Pennsylvania Extirpated, but which subsequently are found to exist in this Commonwealth.

Pennsylvania Extirpated - Plant species believed by the Department [of Conservation and Natural Resources] to be extinct within this Commonwealth. These plants may or may not exist outside the Commonwealth.

Pennsylvania Vulnerable

large yellow lady's slipper Cypripedium pubescens
goldenseal Hydrastis canadensis
ginseng Panax quinquefolium

Pennsylvania Rare

waterhemp ragweed Amaranthus cannabinus
bog-rosemary Andromeda polifolia
shale-barren pussytoes Antennaria virginica
puttyroot Aplectrum hyemale
lobed spleenwort Asplenium pinnatifidum
eastern baccharis Baccharis halimifolia
American sea-rocket Cakile edentula
brown sedge Carex buxbaumii
soft-leaved sedge Carex disperma
slender sedge Carex lasiocarpa
bog sedge Carex paupercula
mountain bugbane Cimicifuga americana
Engelmann's flatsedge Cyperus engelmannii
Schweinitz's flatsedge Cyperus schweinitzii
small waterwort Elatine minima
capitate spike-rush Eleocharis olivacea
creeping snowberry Gaultheria hispidual
thread rush Juncus filiformis
Coville's rush Juncus gymnocarpuc
common labrador-tea Ledum groenlandicum
wild blue lupine Lupinus perennis
Hartford fern Lygodium palmatum
umbrella magnolia Magnolia tripetala
Bayard's malaxis Malaxis bayardii
minniebush Menziesia pilosa
prickly-pear cactus Opuntia humifusa
golden club Orontium aquaticum
fog-fruit Phyla lanceolata
Illinois pondweed Potamogeton illinoensis
flat-leaved pondweed Potamogeton robbinsii
flat-stem pondweed Potamogeton zosteriformis
sand cherry Prunus pumila
buffalo nut Pyrularia pubera
white water-crowfoot Ranunculus trichohyllus
tooth-cup Rotala ramosior
subulate arrow-head Sagittaria subulata
lettice saxofrage Saxifraga micranthidifolia
seaside bluestem Schizachyrium scoparium var. littorale
river bullrush Scirpus fluviatilis
Allegheny stonecrop Sedum telephioides
plain ragwort Senecio anonymus
Tennessee golden-rod Solidago roanesis
sand dropseed Sporobolus cryptandrus
crainfly orchid Tipularia discolor
Carolina tassel-rue Trautvetteria caroliniens
snow trillium Trillium nivale
purple bladderwort Utricularia purpurea
mountain bellwort Uvularia puberula
highbush cranberry Viburnum trilobum
bog mat Wolffiella gladiata
yellow-eyed grass Xyris montana
Indian wild rice Zizania aquatica

Pennsylvania Endangered

white monkshood Aconitum reclinatum
sweet flag Acorus americanus
small-flowered false foxglove Agalinis paupercula
colic-root Aletris farinosa
broad-leaved water plantain Alisma plantago-aquatica var. americana
mountain alder Alnus viridis ssp. crispa
oblong-fruited serviceberry Amelanchier bartramiana
low serviceberry Amelanchier humilis
coastal plain serviceberry Amelanchier obovalis
roundleaf serviceberry Amelanchier sanguinea
long-fruited anemone Anemone cylindrica
single-head pussytoes Antennaria solitaria
hairy rock-cress Arabis hirsuta
Missouri rock-cress Arabis missouriensis
swamp-pink Arethusa bulbosa
leopard's-bane Arnica acaulis
beach wormwood Artemisia campestris ssp. caudata
white milkweed Asclepias variegata
Bradley's spleenwort Asplenium bradleyi
black-stalked spleenwort splenium resiliens
rush aster Aster borealis
bog aster Aster nemoralis
narrow-leaved white-topped aster Aster solidagineus
low showy aster Aster spectabilis
Cooper's milk-vetch Astragalus neglectus
swamp beggar-ticks Bidens bidentoides
aster-like boltonia Boltonia asteroides
wild hyacinth Camassia scilloides
awned sedge Carex atherodes
golden-fruited sedge Carex aurea
Bebb's sedge Carex bebbii
Bicknell's sedge Carex bicknellii
bull sedge Carex bullata
Carey's sedge Carex careyana
Crawford's sedge Carex crawfordii
short hair sedge Carex crinita var. brevicrinis
northeastern sedge Carex cryptolepis
ebony sedge Carex eburnea
handsome sedge Carex formosa
elk sedge Carex garberi
Geyer's sedge Carex geyeri
Mead's sedge Carex meadii
Mitchell's sedge Carex mitchelliana
few-flowered sedge Carex pauciflora
cyperus-like sedge Carex pseudocyperus
backward sedge Carex retrorsa
Richardson's sedge Carex richardsonii
Schweinitz's sedge Carex schweinitzii
Atlantic sedge Carex sterilis
cattail sedge Carex typhina
green sedge Carex viridula
mouse-ear chickweed Cerastium arvense var. villosissimum
slender sea-oats Chasmanthium laxum
Fogg's goosefoot Chenopodium foggii
green-and-gold Chrysogonum virginianum
Maryland golden aster Chrysopsis mariana
horrible thistle Cirsium horridulum
twig rush Cladium mariscoides
vase-vine leather-flower Clematis viorna
mountain pepper-bush Clethra acuminata
butterfly-pea Clitoria mariana
hemlock-parsley Conioselinum chinense
Wister's coral-root Corallorhiza wisteriana
golden corydalis Corydalis aurea
slender rock-brake Cryptogramma stelleri
Fraser's sedge Cymophyllus fraseri
smooth swallow-wort Cynanchum laeve
umbrella flatsedge Cyperus diandrus
Houghton's flatsedge Cyperus houghtonii
reflexed flatsedge Cyperus refractus
small yellow lady's-slipper Cypripedium parviflorum
Laurentian bladder fern Cystopteris laurentiana
tall larkspur Delphinium exaltatum
American beakgrain Diarrhena obovata
wild bleeding-hearts Dicentra eximia
common shooting-star Dodecatheon meadia
mountain wood fern Dryopteris campyloptera
log fern Dryopteris celsa
Walter's barnyard-grass Echinochloa walteri
long-stemmed water-wort Elatine americana
capitate spike-rush Eleocharis caribaea
flat-stemmed spike-rush Eleocharis compressa
slender spike-rush Eleocharis elliptica
spike-rush Eleocharis obtusa var. peasei
dwarf spike-rush Eleocharis parvula
few-flowered spike-rush Eleocharis pauciflora var. fernaldii
four-angled spike-rush Eleocharis quadrangulata
beaked spike-rush Eleocharis rostellata
slender spike-rush Eleocharis tenuis var. verrucosa
elephant's foot Elephantopus carolinianus
downey willow-herb Epilobium strictum
variegated horsetail Equisetum variegatum
scouring rush Equisetum ferrissii
slender cotton-grass Eriophorum gracile
rough cotton-grass Eriophorum tenellum
wild ipecac Euphorbia ipecacuanhae
blunt-leaved spurge Euphorbia obtusata
glade spurge Euphorbia purpurea
cluster fescue Festuca paradoxa
American columbo Frasera caroliniensis
pumpkin ash Fraxinus profunda
Labrador marsh bedstraw Galium labradoricum
box huckleberry Gaylussacia brachycera
dwarf huckleberry Gaylussacia dumosa
soapwort gentian Gentiana saponaria
striped gentian Gentiana villosa
cranesbill Geranium bicknellii
blunt manna-grass Glyceria obtusa
golden-pert Gratiola aurea
Appalachian oak fern Gymnocarpium appalachianum
Bicknell's hoary rockrose Helianthemum bicknellii
common hemicarpa Hemicarpha micrantha
multiflowered mud-plantain Heteranthera multiflora
Maryland hawkweed Hieracium traillii
vanilla sweet-grass Hierochloe odorata
rock clubmoss Huperzia porophila
large-leafed water-leaf Hydrophyllum macrophyllum
purple rocket Iodanthus pinnatifidus
crested dwarf iris Iris cristata
slender blue iris Iris prismatica
dwarf iris Iris verna
Virginia blue flag Iris virginica
small-whorled pogonia Isotria medeoloides
short-fruited rush Juncus brachycarpus
forked rush Juncus dichotomus
bayonet rush Juncus militaris
scirpus-like rush Juncus scirpoides
Torrey's rush Juncus torreyi
marsh pea Lathyrus palustris
narrowleaf bush clover Lespedeza angustifolia
lovage Ligusticum canadense
sandplain wild flax Linum intercursum
grooved yellow flax Linum sulcatum
southern twayblade Listera australis
heart-leaved twayblade Listera cordata
kidney-leaved twayblade Listera smallii
hispid gromwell Lithospermum caroliniense
American gromwell Lithospermum latifolium
brook lobelia Lobelia kalmii
downy lobelia Lobelia puberula
hairy honeysuckle Lonicera hirsuta
swamp fly honeysuckle Lonicera oblongifolia
mountain fly honeysuckle Lonicera villosa
upright primrose-willow Ludwigia decurrens
false loosestrife seedbox Ludwigia polycarpa
wood-rush Luzula bulbosa
foxtail clubmoss Lycopodiella alopecuroides
taper-leaved bugle-weed Lycopus rubellus
stagger-bush Lyonia mariana
winged loosestrife Lythrum alatum
white adder's-mouth Malaxis brachypoda
large-flowered marshallia Marshallia grandiflora
oblique milkvine Matelea obliqua
heart-leafed meehania Meehania cordata
Beck's water-marigold Megalodonta beckii
naked bishop's-cap Mitella nuda
spotted bee-balm Monarda punctata
Chamisso's miner's-lettuce Montia chamissoi
false dropseed muhly Muhlenbergia uniflora
northern water-milfoil Myriophyllum exalbescens
Farwell's water-milfoil Myriophyllum farwellii
broad-leaved water-milfoil Myriophyllum heterophyllum
whorled water-milfoil Myriophyllum verticillatum
holly-leaved naiad Najas marina
American lotus Nelumbo lutea
false gromwell Onosmodium hispidissimum
limestone adder's-tongue Ophioglossum engelmannii
slender mountain-ricegrass Oryzopsis pungens
southern sea-beach panic-grass Panicum amarum var. amarulum
annulus panic-grass Panicum annulum
panic-grass Panicum commonsianum var. euchlamydeum
panic-grass Panicum laxiflorum
shining panic-grass Panicum lucidum
velvety panic-grass Panicum scoparium
acuminate dichanthelium Panicum spretum
slender panic-grass Panicum xanthophysum
Carolina grass-of-parnassus Parnassia glauca
forked chickweed Paronychia fastigiata var. nuttallii
passion-flower Passiflora lutea
Canby's mountain-lover Paxistima canbyi
swamp lousewort Pedicularis lanceolata
mountain phlox Phlox ovata
downy phlox Phlox pilosa
moss pink Phlox subulata ssp. brittonii
Carolina leaf-flower Phyllanthus caroliniensis
Virginia ground-cherry Physalis virginiana
leafy white orchid Platanthera dilatata
Hooker's orchid Platanthera hookeri
leafy northern green orchid Platanthera hyperborea
shrubby camphor-weed Pluchea odorata
autumn bluegrass Poa autumnalis
Jacob's-ladder Polemonium van-bruntiae
cross-leaved milkwort Polygala cruciata
Curtis's milkwort Polygala curtissii
pink milkwort Polygala incarnata
bitter milkwort Polygala polygama
eastern jointweed Polygonella articulata
Carey's smartweed Polygonum careyi
swamp smartweed Polygonum setaceum var. interjectum
Braun's holly fern Polystichum braunii
balsam poplar Populus balsamifera
Fries' pondweed Potamogeton friesii
grassy pondweed Potamogeton gramineus
Hill's pondweed Potamogeton hillii
Oakes' pondweed Potamogeton oakesianus
blunt-leaved pondweed Potamogeton obtusifolius
white-stemmed pondweed Potamogeton praelongus
spotted pondweed Potamogeton pulcher
narrow-leaved pondweed Potamogeton strictifolius
Tennessee pondweed Potamogeton tennesseensis
Vasey's pondweed Potamogeton vaseyi
shrubby cinquefoil Potentilla fruticosa
bushy cinquefoil Potentilla paradoxa
three-toothed cinquefoil Potentilla tridentata
rattlesnake-root Prenanthes crepidinea
beach plum Prunus maritima
southern mountain-mint Pycnanthemum pycnanthemoides
Torrey's mountain-mint Pycnanthemum torrei
southern red oak Quercus falcata
willow oak Quercus phellos
Shumard's oak Quercus shumardii
tufted buttercup Ranunculus fascicularis
low spearwort Ranunculus pusillus
lanceolate buckthorn Rhamnus lanceolata
Maryland meadow-beauty Rhexia mariana
dwarf azalea Rhododendron atlanticum
capillary beaked-rush Rhynchospora capillacea
bristly black currant Ribes lacustre
Missouri gooseberry Ribes missouriense
sand blackberry Rubus cuneifolius
fringed-leaved petunia Ruellia humilis
long-lobed arrow-head Sagittaria calycina var. spongiosa
hoary willow Salix candida
Carolina willow Salix caroliniana
bog-willow Salix pedicellaris
slender willow Salix petiolaris
pineland pimpernel Samolus parviflorus
pod-grass Scheuchzeria palustris
hard-stemmed bullrush Scirpus acutus
Smith's bullrush Scirpus smithii
Torrey's bullrush Scirpus torreyi
minor nutrush Scleria minor
reticulated nutrush Scleria reticularis
whorled nutrush Scleria verticillata
rock skullcap Scutellaria saxatilis
showy skullcap Scutellaria serrata
roseroot stonecrop Sedum rosea
cat's-paw ragwort Senecio antennariifolius
Canada buffalo-berry Shepherdia canadensis
sida Sida hermaphrodita
eastern blue-eyed grass Sisyrinchium atlanticum
Harris' goldenrod Solidago arguta var. harrissii
Curtis' goldenrod Solidago curtisii
slender goldenrod Solidago erecta
stiff goldenrod Solidago rigida
sticky goldenrod Solidago spathulata var. racemosa
showy mountain-ash Sorbus decora
branching bur-reed Sparganium androcladum
Case's ladies'-tresses Spiranthes casei
October ladies'-tresses Spiranthes ovalis
hooded ladies'-tresses Spiranthes romanzoffiana
spring ladies'-tresses Spiranthes vernalis
rough dropseed Sporobolus clandestinus
prairie dropseed Sporobolus heterolepis
Nuttall's hedge-nettle Stachys nuttallii
white twisted-stalk Streptopus amplexifolius
pencil-flower Stylosanthes biflora
mountain pimpernel Taenidia montana
thick-leaved meadow-rue Thalictrum coriaceum
eared false-foxglove Tomanthera auriculata
Ohio spiderwort Tradescantia ohiensis
blue-curls Trichostema setaceum
Kate's mountain clover Trifolium virginicum
horse-gentian Triosteum angustifolium
nodding pogonia Triphora trianthophora
purple sandgrass Triplasis purpurea
gamma grass Tripsacum dactyloides
narrow false oats Trisetum spicatum
spreading globe flower Trollius laxus
floating bladderwort Utricularia radiata
tawny ironweed Vernonia glauca
possum haw viburnum Viburnum nudum
coast violet Viola brittoniana
prairie violet Viola pedatifida
possum grape Vitis cinerea var. baileyana
sand grape Vitis rupestris
New England grape Vitis novae-angliae
death-camas Zigadenus elegans var. glaucus

Pennsylvania Extirpated

two-seeded copperleaf Acalypha deamii
sensitive joint-vetch Aeschynomene virginica
blue-ridge false-foxglove Agalinis decemloba
tall bentgrass Agrostis altissima
bearberry manzanita Arctostaphylos uva-ursi
red milkweed Asclepias rubra
American barberry Berberis canadensis
bluehearts Buchnera americana
crowded sedge Carex adusta
Fernald's hay sedge Carex aenea
Rocky Mountain sedge Carex backii
Barratt's sedge Carex barrattii
creeping sedge Carex chordorrhiza
shore-line sedge Carex hyalinolepis
Sartwell's sedge Carex sartwellii
Atlantic white cedar Chamaecyparis thyoides
slender day-flower Commelina erecta
Virginia day-flower Commelina virginica
pink tickseed Coreopsis rosea
water pigmy-weed Crassula aquatica
elliptical rushfoil Crotonopsis elliptica
northern hound's-tongue Cynoglossum boreale
many-spiked flatsedge Cyperus polystachyos
retrorse flatsedge Cyperus retrorsus
small white lady's-slipper Cypripedium candidum
sessile-leaved tick-trefoil Desmodium sessilifolium
fir clubmoss Diphasiastrum sabinifolium
sea-shore salt-grass Distichlis spicata
Carolina whitlow-grass Draba reptans
smooth coneflower Echinacea laevigata
three-ribbed spike-rush Eleocharis tricostata
long-tubercled spike-rush Eleocharis tuberculosa
Schweinitz's waterweed Elodea schweinitzii
sugarcane plumegrass Erianthus giganteus
ten-angle pipewort Eriocaulon decangulare
Parker's pipewort Eriocaulon parkeri
marsh eryngo Eryngium aquaticum
white thoroughwort Eupatorium album
white-bracted thoroughwort Eupatorium leucolepis
hairy fimbry Fimbristylis puberula
eastern milk-pea Galactia regularis
downy milk-pea Galactia volubilis
yellow gentian Gentiana alba
Elliott's gentian Gentiana catesbaei
lesser fringed gentian Gentianopsis procera
oak fern Gymnocarpium heterosporum
broad-leaved beardgrass Gymnopogon ambiguus
creeping bluets Hedyotis michauxii
swamp sunflower Helianthus angustifolius
little barley Hordeum pusillum
American featherfoil Hottonia inflata
mountain clubmoss Huperzia selago
many-flowered pennywort Hydrocotyle umbellata
creeping St. John's-wort Hypericum adpressum
coppery St. John's-wort Hypericum denticulatum
nits-and-lice Hypericum drummondii
clasping-leaved St. John's-wort Hypericum gymnanthum
St. Peter's-wort Hypericum stans
ink-berry Ilex glabra
Virginia willow Itea virginica
Greene's rush Juncus greenei
junegrass Koeleria cristata
sand-myrtle Leiophyllum buxifolium
little water duckweed Lemna obscura
pale duckweed Lemna valdiviana
tall bushclover Lespedeza stuevei
awl-shaped mudwort Limosella australis
Nuttall's lobelia Lobelia nuttallii
spherical-fruited seedbox Ludwigia sphaerocarpa
Nuttall's mud-flower Micranthemum micranthemoides
short muhly Muhlenbergia capillaris
Virginia false-gromwell Onosmodium virginianum
southeastern adder's tongue Ophioglossum pycnostichum
cloaked panic-grass Panicum commonsianum var. commonsianu
Leiberg's panic-grass Panicum leibergii
American fever-few Parthenium integrifolium
Florida beadgrass Paspalum floridanum var. glabratum
Christmas mistletoe Phoradendron serotinum
black oatgrass Piptochaetium avenaceum
crested yellow orchid Platanthera cristata
prairie white-fringed orchid Platanthera leucophaea
yellow milkwort Polygala lutea
bushy knotweed Polygonum ramosissimum
swamp cottonwood Populus heterophylla
northern pondweed Potamogeton alpinus
threadleaf pondweed Potamogeton filiformis
glaucous rattlesnake-root Prenanthes racemosa
comb-leaved mermaid-weed Proserpinaca pectinata
mock bishop-weed Ptilimnium capillaceum
hairy mountain-mint Pycnanthemum pilosum
creeping spearwort Ranunculus flammula
long-stalked crowfoot Ranunculus hederaceus
prairie coneflower Ratibida pinnata
flame azalea Rhododendron calendulaceum
brown beaked-rush Rhynchospora fusca
beaked-rush Rhynchospora gracilenta
Carolina petunia Ruellia caroliniensis
heart sorrel Rumex hastatulus
slender marsh pink Sabatia campanulata
arrow-head Sagittaria stagnorum
slender bullrush Scirpus heterochaetus
prairie ragwort Senecio plattensis
blue-eyed-grass Sisyrinchium albidum
sand blue-eyed grass Sisyrinchium arenicola
long-stalked greenbrier Smilax pseudochina
small bur-reed Sparganium minimum
Virginia spiraea Spiraea virginiana
ladies'-tresses Spiranthes magnicamporum
slender ladies'-tresses Spiranthes tuberosa
hyssop hedge-nettle Stachys hyssopifolia
buffalo clover Trifolium reflexum
marsh arrowgrass Triglochin palustre
fibrous bladderwort Utricularia fibrosa
northeastern bladderwort Utricularia resupinata
kidney-leaved white violet Viola renifolia
three-parted violet Viola tripartita

Appendix 2
Pennsylvania Noxious Weeds
(based on Noxious Weed Control Committee recommendations, 1994).

marijuana Cannabix sativa few scattered localities
nodding thistle Carduus nutans central & SE PA
Canada thistle Cirsium arvense common throughout state
bull thistle Cirsium vulgare common throughout state
jimsonweed Datura stramonium mostly S half of state
purple Lythrum salicaria wetlands in many parts
loosestrife of state    
mile-a-minute Polygonum mainly southeastern PA
weed perfoliatum  
kudzu Pueraria lobata documented from SE PA & Allegheny Co.
multiflora rose Rosa multiflora throughout state, often planted
shattercane Sorghum bicolor scattered, mainly easter ssp. drummondii PA
Johnsongrass Sorghum primarily eastern PA