Composition of the Wisconsin Flora

Native taxa

Plants native to Wisconsin refers to those assumed to have been present in some part of Wisconsin prior to European settlement, whereas introduced taxa were brought into our state, intentionally or unintentionally, from the outside, usually from Europe or Eurasia or other parts of North America. Thus, "introduced" taxa in the Checklist are believed to be non-native in Wisconsin even though they may be native in nearby states or elsewhere on this continent. Because it is often difficult and sometimes impossible to determine whether a plant is native or introduced, taxonomists sometimes disagree. For most taxa the status reported here is that in Gray's Manual (Fernald 1950), although for a few taxa we follow Gleason and Cronquist (1991), Voss (1972, 1985, 1996), or our own judgment. Sometimes there is considerable overlap among the native and non-native categories. For example, Calylophus serrulatus (Nutt.) P. H. Raven is both native and adventive in different parts of the state; Galium aparine L., Plantago rugelii Decne., and possibly Portulaca oleracea L. are both native and naturalized or have both native and naturalized races; and Gleditsia triacanthos L. is both native and escaped.

At least five species are considered extirpated in Wisconsin: Asclepias meadii Torr. ex A. Gray - Mead's milkweed, Collinsia verna Nutt. - eastern blue-eyed-Mary, Eleocharis equisetoides (Elliott) Torr. - knotted spike-rush, Sassafras albidum (Nutt.) Nees - sassafras, and Tomanthera auriculata (Michx.) Raf. - eared false foxglove. Unfortunately, there are many other native taxa which, due primarily to loss of habitat, are either endangered (64) or threatened (57) within Wisconsin or have not been collected here for many years. In addition, there are 152 taxa of such low frequency of occurrence as to warrant special concern. These taxa are indicated in the Checklist by the following categories, which are used by the BER, Wisconsin DNR in their "Wisconsin Natural Heritage Working List" (dated 03/17/99).

• Endangered (END) – Wisconsin Endangered Species: any species whose continued existence as a viable component of the state’s wild animals or wild plants is determined by the Department [Wisconsin DNR] to be in jeopardy on the basis of scientific evidence (statute 29.604).
• Threatened (THR) – Wisconsin Threatened Species: any species which appears likely, within the foreseeable future, on the basis of scientific evidence to become endangered (statute 29.604).
• Special Concern (SC) – Species about which some problem of abundance or distribution is suspected but not yet proved. The main purpose of this category is to focus attention on certain species before they become threatened or endangered.

Among publications on plant taxonomy by different authors, even those working within the same state, there may be differences of opinion as to the generic placement of a species, the rank at which any taxon is accepted, the acceptance or not of a species or of infraspecific taxa within a species, and the native or non-native status of a taxon. Differences between this Checklist and the Wisconsin Natural Heritage Working List (which lists 73 taxa as endangered, 65 as threatened, and 187 as special concern) are given in Table 2. Taxa which are accepted on the Working List but which are considered synonyms in this Checklist are listed under their accepted taxa, and their BER protection category is also given. As an example:

Packera indecora (Greene) A.Löve & D.Löve
   plains ragwort, rayless ragwort, taller discoid groundsel
   Senecio indecorus Greene
   Native (A Synonym is Listed as Threatened by WI DNR)

There are three species, Dodecatheon radicatum Greene, Onosmodium molle Michx., and Ophioglossum vulgatum L., which are listed by the BER as Special Concern taxa, but are not accepted in the Checklist as occurring in Wisconsin. Although these are still considered "good" species with ranges outside of Wisconsin, the Wisconsin entities previously ascribed to these species are now considered to be either distinct species (Dodecatheon amethystinum (Fassett) Fassett and Ophioglossum pusillum Raf.) in their own right, or have been transferred to another species (the two Wisconsin infraspecific taxa treated formerly under Onosmodium molle are now accepted as varieties of O. bejariense A. DC).

Because the Wisconsin Natural Heritage Working List is revised quite frequently, it is our intention to keep the electronic version of the Checklist always current with the most recent Working List. A printed copy of The Wisconsin Natural Heritage Working List is available from the Wisconsin Natural Heritage Program, Bureau of Endangered Resources, DNR, Box 7921, Madison, WI 53707 or electronically at http://www.dnr.state.wi.us/org/land/er/biodiversity.htm.

Table 2. Differences between Bureau of Endangered Resources (BER) listing of taxa and the current Checklist.

                     BER Taxa                                                      CHECKLIST Taxa

BER taxa with change in generic placement in Checklist:
 

SC Cacalia muhlenbergii = Arnoglossum reniforme THR Cacalia tuberosa = Arnoglossum plantagineum SC Cassia marilandica = Senna marilandica THR Elymus lanceolatus subsp. psammophilus = Elytrigia dasystachya subsp. psammophila SC Euphorbia polygonifolia = Chamaesyce polygonifolia SC Hedyotis caerulea = Houstonia caerulea SC Lycopodium porophilum = Huperzia porophila SC  Lycopodium selago = Huperzia selago END Moehringia macrophylla = Arenaria macrophylla SC Nothocalais cuspidata = Microseris cuspidata THR  Potamogeton vaginatus = Stuckenia vaginata THR Psilocarya scirpoides = Rhynchospora scirpoides SC  Psoralea argophylla = Pediomelum argophyllum SC Psoralea esculenta = Pediomelum esculentum END Scirpus hallii = Schoenoplectus hallii SC Scirpus torreyi = Schoenoplectus torreyi THR Senecio indecorus = Packera indecora SC  Senecio plattensis =Packera plattensis

  BER taxa with change in rank in Checklist:
 

THR

Gnaphalium obtusifolium var. saxicola

= Gnaphalium saxicola

SC

Littorella americana

= Littorella uniflora var. americana

SC

Malaxis brachypoda

= Malaxis monophyllos var. brachypoda

SC

Onosmodium molle subsp. hispidissimum

= Onosmodium bejariense var. hispidissimum

SC

Sagittaria calycina

= Sagittaria montevidensis subsp. calycina

THR

Valeriana sitchensis subsp. uliginosa

= Valeriana uliginosa

SC

Viburnum cassinoides

= Viburnum nudum var. cassinoides

SC

Woodsia oregana var. cathcartiana

= Woodsia oregana subsp. cathcartiana

BER taxa with change in rank and generic placement in Checklist:
 

SC

Minuartia dawsonensis

=Arenaria stricta subsp. dawsonensis

BER infraspecific taxa not accepted in Checklist:
 

SC	Arabis missouriensis var. deamii					= Arabis missouriensis
SC	Carex pallescens var. neogaea					= Carex pallescens
SC	Diodia teres var. teres					= Diodia teres
SC	Dryopteris fragrans var. remotiuscula					= Dryopteris fragrans
END	Ranunculus gmelinii var. hookeri					= Ranunculus gmelinii

BER taxa placed in synonymy in Checklist:
 

THR	Aconitum noveboracense	= Aconitum columbianum supsp. columbianum
END	Anemone multifida var. hundsoniana	= Anemone multifida var. multifida
END	Asplenium viride	= Asplenium trichomanes-ramosum
SC	Carex artitecta	= Carex albicans var. albicans
END	Carex media	= Carex norvegica subsp. inferalpina
END	Draba lanceolata	= Draba cana
SC	Echinodorus rostratus	= Echinodorus berteroi var. lanceolatus
SC	Eclipta alba	= Eclipta prostrata
SC	Osmorhiza chilensis	= Osmorhiza berteroi
SC	Potamogeton capillaceus	= Potamogeton diversifolius
END	Viola fimbriatula	= Viola sagittata var. ovata

Species with one or more infraspecific taxa in Checklist but only listed at the species level by BER:
 

SC

Asplenium trichomanes

END

Lonicera involucrata

END

Astragalus alpinus

THR

Opuntia fragilis

END

Astragalus crassicarpus

END

Orobanche ludoviciana

SC

Calamagrostis stricta

THR

Parnassia palustris

THR

Calypso bulbosa

SC

Phlox bifida

SC

Cardamine pratensis

SC

Platanthera dilatata

THR

Carex lenticularis

SC

Platanthera orbiculata

SC

Clematis occidentalis

SC

Ptelea trifoliata

SC

Dalea villosa

SC

Rhus aromatica

SC

Deschampsia cespitosa

THR

Ribes oxyacanthoides

SC

Eleocharis compressa

THR

Salix planifolia

SC

Eleocharis olivacea

SC

Scutellaria ovata

SC

Equisetum variegatum

SC

Streptopus amplexifolius

END

Fimbristylis puberula

THR

Tofieldia glutinosa

SC

Gymnocarpium jessoense

SC

Triphora trianthophora

END

Juncus stygius

Taxa considered native by BER but considered non-native in Checklist:
 

SC	Cirsium flodmanii	Adventive
END	Diarrhena americana	Excluded
SC	Galium palustre	Locally established
SC	Hibiscus moscheutos subsp. moscheutos	Escaped
SC	Peltandra virginica	Locally established
SC	Penstemon tubaeflorus	Adventive

Non-native taxa

The status of non-native species often presents problems. The Native American Indians introduced species from the South and West. More recent immigrants from Europe, Asia, and Africa have introduced many more species. Each introduced plant has its unique history (mostly unknown), and each has a status at some point along the continuum from being firmly established to being an ephemeral, one-time waif.

Terms used to describe the status of introduced taxa are less precisely defined than "native." Introduced plants include those which were planted originally and now have spread (e.g., Populus alba L.) or become naturalized (e.g., Phleum pratense L.), as well as adventive species which have escaped from cultivation (e.g., Asparagus officinalis L.), established themselves as unwanted weeds (e.g., Malva rotundifolia L.), or appeared as occasional waifs (e.g., Camelina sativa (L.) Crantz). A few ornamentals (Delphinium elatum L.), medicinal and culinary herbs (Anethum graveolens L.), and crop plants (Sorghum bicolor (L.) Moench) are included, although they probably are not truly established, and others (Agrostemma githago L., once common in rye fields) are probably no longer extant in the state. The naturalized and adventive plants, whether generally or locally distributed, are listed because they occur in Wisconsin. The marginal plants, including not only those recently arrived, but also those that may have disappeared, are listed because they are part of the historical record, and like presumed extinct native species, may one day be rediscovered. Whatever the case, this book includes all vascular plants that occur in Wisconsin in the sense of their being represented by a herbarium specimen from a plant growing "wild." Although some may find this policy too liberal, assembling all such records into the present text has made the Checklist a more useful reference, one which reflects the continuing movement and changing frequency of species in the landscape. The status of each non-native taxon is given within the Checklist. As with native status, there is often substantial overlap between the various non-native status categories. For example, Setaria italica (L.) P. Beauv. is widespread and weedy, but it originally escaped from cultivation.

Determining the status is particularly problematical for a taxon that is based on a single or a few herbarium records, because often the label gives no indication as to whether the plant was cultivated or appeared to be native, naturalized, escaped, or a waif. We used our best judgment when deciding which records should be accepted and how each taxon should be classified.

• Introduced – adventive: only casually established from a native or naturalized source or disseminated from a more distant area; neither naturalized nor persistent.
• Introduced – escaped: normally cultivated, but established (i.e., growing and reproducing) where not planted.
• Introduced – locally established: naturalized at particular places in small or large numbers.
• Introduced – naturalized: well established, often widespread.
• Introduced – persisting and spreading: garden plants expanding only slightly or escaped only slightly beyond the area in which they were originally planted.
• Introduced – rarely escaped: spreading vegetatively or by seed from cultivated plants, but seldom encountered.

Ecologically Invasive Plants

Only three species in Wisconsin are legally designated "noxious" weeds. By municipal law [statute 66.96], "Every person shall destroy [complete killing of weeds . . . in such a manner as will effectually prevent such plants from maturing to the bloom or flower stage] all noxious weeds on all lands which he shall own, occupy or control." They are Cirsium arvense (L.) Scop. - Canada thistle, Convolvulus arvensis L. - field bindweed, and Euphorbia esula L. - leafy spurge. There are two other species, Lythrum salicaria L. - purple loosestrife ("or hybrids thereof") and Rosa multiflora Thunb. ex Murray - multiflora rose, which are legally [municipal law statute 66.955] listed as "nuisance weeds." Propagation of nuisance weeds is prohibited by statute: "Except as provided in sub (3), no person may sell, offer for sale, distribute, plant or cultivate any nuisance weed or seeds thereof." Not surprisingly, the taxa that have received legal recognition as problem species have a large negative economic impact on the state’s agricultural enterprises. There are numerous other weedy species, including some roadside "wildflowers," that pose a potentially serious economic threat to agricultural lands and gardens.

There are many other invasive or potentially invasive taxa present in the state, which are or could become ecologically important pests in natural habitats. As defined by the Wisconsin DNR, "Most invasive species are ecological pioneers and colonizers which, once introduced, quickly establish themselves in ecologically disturbed communities. Invasive species typically displace native flora due to faster growth rates, efficient dispersal mechanisms, and tolerance of a wider range of conditions. Invasive species often lack natural predators and diseases which control populations in their native environments..." (http://www.dnr.state.wi.us/org/land/er/invasive/intro.htm, 1999).

Non-native species that are currently considered as invasive or potentially invasive in Wisconsin natural areas by the Wisconsin DNR are indicated in the Checklist by one of two invasive categories. For each such taxon in the Checklist, the invasive category is given after the taxon’s non-native status category. These invasive categories are defined as:

• Ecologically invasive: able to invade wild areas and outcompete native species, degrading habitats and causing extensive ecological damage.
• Potentially invasive: constituting a serious problem in other parts of the Midwest and which may become troublesome in Wisconsin, or currently invasive outside of natural areas in Wisconsin.

There are also a number of opportunistic native taxa, colonizers which can come to dominate natural areas due to disturbance or suppression of natural processes, such as fire. These species are also noted in the Checklist by an invasive status, "Native - potentially invasive." For a thorough review of the ecologically invasive species and for suggested control methods, see Hoffman and Kearns (1997) and http://www.dnr.state.wi.us/org/land/er/invasive_species.htm.

Summary of the Wisconsin Flora

Table 5. Number of native and introduced families and genera in Wisconsin*.