Arboretum, University of Wisconsin-Madison http://uwarboretum.org/
Botanical Club of Wisconsin (BCW) https://sites.google.com/site/botanicalclubofwisconsin/
Ecological Landscapes of Wisconsin http://dnr.wi.gov/topic/landscapes/
A Field Guide to Invasive Plants in Wisconsin http://dnr.wi.gov/files/pdf/pubs/fr/fr0436a.pdf
Gathering Waters Conservancy http://www.gatheringwaters.org/
Invasive Plants Association of Wisconsin (IPAW) http://www.ipaw.org/
The Nature Conservancy, Wisconsin Chapter
Trees of Wisconsin http://www.uwgb.edu/biodiversity/herbarium/trees/tree_intro01.htm
Wisconsin Department of Natural Resources http://dnr.wi.gov/
Aquatic and Wetland Vascular Plants of the Northern Great Plains https://www.fs.usda.gov/treesearch/pubs/30420
Barron, G. 1999. Mushrooms of Northeast North America: Midwest to New England. Lone Pine Field Guide. [comprehensive field guide and includes Wisconsin species with keys]
Case, F., Jr. 1987. Orchids of the western Great Lakes region. Cranbrook Press.
Chadde, S. W. 1998. A Great Lakes Wetland Flora. Pocketflora Press, Calumet, MI.
Crow, G. E. & C. B. Hellquist. 2000. Aquatic and Wetland Plants of Northeastern North America. University of Wisconsin Press.
Farrar, J. L. 1995. Trees of the Northern United States and Canada. Iowa State University Press. Ames, IA.
Gleason, H. A. & A. Cronquist 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. 2nd ed. The New York Botanical Garden, Bronx, NY.
Holmgren, N. H. 1998. Illustrated Companion to Gleason and Cronquist’s Manual. The New York Botanical Garden, Bronx, NY.
Lahring, H. 2003. Water and wetland plants of the Prairie Provinces. University of Regina.
Leopold, D. J. et al., 1998. Trees of the Central Hardwood Forests of North America: An identification and cultivation guide. Timber Press.
Newmaster, S., A. Harris, & L. Kershaw. 1997. Wetland plants of Ontario. Lone Pine Publishing.
Skawinski, P. M. 2011. Aquatic Plants of the Upper Midwest: A photographic field guide to our underwater forests. Self published.
Smith, W. 2008. Trees and Shrubs of Minnesota. University of Minnesota Press.
Swink, F. & G. Wilhelm. 1994. Plants of the Chicago region. 4th ed. Indiana Academy of Science. Indianapolis, IN.
Tom Volk’s Fungi http://botit.botany.wisc.edu/toms_fungi/
Vance, F. R. et al., 1999. Wildflowers of the Northern Great Plains. 3rd ed. University of Minnesota Press.
Voss, E. G. & A. Reznicek. 2012. Field Manual of Michigan Flora. University of Michigan Press. [contains much of the flora of WI; there is no comparable reference for WI]
Picture Guides and Specialty Books
Bennett, J. Lichens of Wisconsin https://herbarium.wiscweb.wisc.edu/wp-content/uploads/sites/205/2017/10/lichens-of-wi-web-20170515.pdf
Black, M. R. & E. J. Judziewicz. 2009. Wildflowers of Wisconsin and the Great Lakes Region: A comprehensive Field Guide. 2nd ed. University of Wisconsin Press.
Borman, S., R. et al. 1997. Through the Looking Glass… A Field Guide to Aquatic Plants. Wisconsin DNR Publication FH-207-97.
Cochrane, T. S. & H. H. Iltis. 2000. Atlas of the Wisconsin Prairie and Savanna Flora. http://digital.library.wisc.edu/1711.dl/EcoNatRes.DNRBull191
Cochrane, T. S., et al. 2006. Prairie Plants of the University of Wisconsin-Madison Arboretum: Including horsetails, ferns, rushes, sedges, grasses, shrubs, vines, weeds, and wildflowers. University of Wisconsin Press.
Eggers, S.D. and D.M. Reed. 2011. Wetland Plants and Plant Communities of Minnesota and Wisconsin, 3nd ed.. U.S. Army Corps of Engineers, St. Paul MN. https://usace.contentdm.oclc.org/digital/collection/p266001coll1/id/2801/
Fassett, N. C. 1957. A Manual of Aquatic Plants. The University of Wisconsin Press, Madison, WI
Fassett, N. C. 1976. Spring Flora of Wisconsin. 4th ed. The University of Wisconsin Press, Madison, WI.
Hipp, S. L. 2008. Field Guide to Wisconsin Sedges. University of Wisconsin Press, Madison, WI.
Nichols, S. & R. Martin. 1990. Wisconsin lake plant distribution. Information Circular 69. Wisconsin Geological and Natural History Survey.
Nichols, S. 1999. Distribution and habitat descriptions of Wisconsin lake plants. Bulletin 96. Wisconsin Geological and Natural History Survey.
Herbaria (designated herbarium code)
Green Bay: Cofrin Center for Biodiversity, Herbarium, University of Wisconsin-Green Bay http://www.uwgb.edu/biodiversity/herbarium/
Madison (CFMR): Center for Forest Mycology Research, Herbarium & Culture Center, University of Wisconsin – Madison http://www.fpl.fs.fed.us/search/mycology_request.php
Madison (MAD): Center for Wood Anatomy Research, University of Wisconsin – Madison http://www.fpl.fs.fed.us/research/centers/woodanatomy/
Madison (WIS): WisFlora (WI Vascular Plant Species), State Herbarium, University of Wisconsin – Madison http://www.botany.wisc.edu/wisflora/
Milwaukee (MIL): Milwaukee Public Museum, Section for Botany
Milwaukee (UWM): University of Wisconsin-Milwaukee & UWM Field Station Herbaria http://www4.uwm.edu/letsci/biologicalsciences/facilities/herbarium/
La Crosse (UWL): University of Wisconsin-La Crosse Herbarium
Stevens Point (UWSP): Freckmann Herbarium – University of Wisconsin-Stevens Point
Botany Department, University of Wisconsin-Madison http://www.botany.wisc.edu/
Curtis, J. T. 1959. The vegetation of Wisconsin: An ordination of plant communities. University of Wisconsin Press.
Encyclopedia of Life http://eol.org/
Flora of North America online
Hoffman, R. 2002. Wisconsin's Natural Communities. University of Wisconsin Press.
Miller, M., K. Songer, & R. Dolen. 2014. Field guide to Wisconsin streams. University of Wisconsin Press.
Mushroom Observer http://mushroomobserver.org/
Regional Supplements to the Army Corps of Engineers USACE) Wetland Delineation Manual http://www.usace.army.mil/missions/civilworks/regulatoryprogramandpermits/reg_supp.aspx [Wisconsin is in two supplemental regions]
USACE North American Digital Flora: National Wetland Plant List http://rsgisias.crrel.usace.army.mil/NWPL/index.html
USDA/NRCS PLANTS Database http://plants.usda.gov/java/
Waller, D. M. & Rooney, T. P. 2008. The Vanishing Present: Wisconsin's Changing Lands, Waters and Wildlife. Univ of Chicago Press.