There are so many great gardening resources and references! Below is a list compiled by Master Gardener colleagues and Horticulture Extension Educators.
UNIVERSITY OF MINNESOTA
Yard & Garden http://www.extension.umn.edu/garden
Food, Health and Nutrition (includes preservation) https://extension.umn.edu/food-health-and-nutrition
Forest Resources https://www.forestry.umn.edu/
Forest Resources Nursery and Lab Trees, shrubs and vine database https://trees.umn.edu/plant-database
Fruits http://fruit.cfans.umn.edu/
How to find help with landscaping https://extension.umn.edu/lawns-and-landscapes/landscape-design
How to hire a tree professional https://extension.umn.edu/find-plants/trees-and-shrubs
Master Gardener Program http://www.extension.umn.edu/garden/master-gardener/
My Minnesota Woods http://www.myminnesotawoods.umn.edu/
Plant Elements of Design plant selection database http://landscapeplants.extension.umn.edu/
Plants for MN Bees https://www.beelab.umn.edu/bees/flowers/plants-mn-bees
Public Gardens of Minnesota https://mngardens.horticulture.umn.edu/
Wild Bee Nests, UMN Bee Lab https://www.beelab.umn.edu/wild-bees/wild-bees-and-houses
ASSOCIATIONS, PUBLIC GARDENS & INSTITUTES
American Horticulture Society (AHS) http://www.ahs.org/
American Public Garden Association http://www.publicgardens.org/
Blue Thumb http://www.blue-thumb.org/
International Society of Arboriculture http://www.isa-arbor.com/
Minnesota State Horticultural Society http://www.northerngardener.org
Missouri Botanic Garden http://www.mobot.org/
West Metro Alliance http://www.westmetrowateralliance.org/
Wild Ones http://www.wildones.org/connect/chapters/minnesota-chapters/
GOVERNMENT AGENCIES & OTHER UNIVERSITY EXTENSION
Cornell University Extension – Garden-based Learning https://gardening.cals.cornell.edu/
Cornell VegMD http://plantclinic.cornell.edu/vegmdfactsheets.html
Minnesota Department of Health – Environments & Your Health http://www.health.state.mn.us/macros/topics/environment.html
Minnesota Department of Natural Resources http://www.dnr.state.mn.us/nr/
Minnesota State Horticultural Society (MSHS) http://www.northerngardener.org/
Minnesota Nursery & Landscape Association (MNLA) http://www.gardenminnesota.com/
National Center for Home Food Preservation https://nchfp.uga.edu/
National Pesticide Information Center http://npic.orst.edu/
University of North Dakota – Lawns, Gardens and Trees https://www.ag.ndsu.edu/horticulture
University of Wisconsin Extension Horticulture https://hort.uwex.edu/
US Department of Agriculture plant database http://plants.usda.gov/
US Department of Agriculture cold hardiness map https://planthardiness.ars.usda.gov/PHZMWeb/
OTHER RESOURCES
ASPCA Toxic and Non-Toxic Plants for Pets http://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants
Minnesota Wildflowers https://www.minnesotawildflowers.info/
National Tree Benefit Calculator http://www.treebenefits.com/calculator/index.cfm
Seed Savers http://www.seedsavers.org/
INVASIVE SPECIES
MN Department of Agriculture Noxious Weed List https://www.mda.state.mn.us/plants-insects/minnesota-noxious-weed-list
MNDNR Invasive Species in Minnesota (Aquatic and terrestrial) https://www.dnr.state.mn.us/invasives/index.html
BOOKS & ONLINE PUBLICATIONS
Capon, B. Botany for Gardeners, 3rd edition, Brian Capon, Portland, OR. 2012.
Cranshaw, W., Garden Insects of North America, Princeton University Press, Princeton, NJ. 2004.
Dewolf, G., Taylor’s Guide to Houseplants, Taylor’s Gardening Guides, 1987.
Dirr, M. A., Manual of Woody Landscape Plants. Stipes Publishing, LLC., Champaign, IL. 1998.
DiSabato-Aust, Tracy, The Well-Tended Perennial Garden. Timber Press, Inc., Portland OR. 2000.
Gleason, M. et al., Diseases of Herbaceous Perennials, APS Press, St. Paul, MN. 2009.
Gordon, D., Growing Fruit in the Upper Midwest, University of Minnesota Press. 1997.
Hahn, J., Insects of the Northwoods, Kollath + Stensas Publishing, Duluth, MN. 2009.
Heger, M. et al., Growing Perennials in Cold Climates, University of Minnesota Press, Minneapolis, MN. 1998, 2011.
Henderson, C., Landscaping for Wildlife, Minnesota Department of Natural Resources. 1987.
Holm, Heather, Pollinators of Native Plants, Pollination Press LLC, Minnetonka, MN. 2014
Hoss, R. et al., Growing Roses in Cold Climates, University of Minnesota Press, Minneapolis, MN. 2012.
Lonnee, D. et al., Growing Shrubs and Small Trees in Cold Climates, University of Minnesota Press, Minneapolis, MN. 2011.
Meyer, M. et al., The Best Plants for 30 Tough Sites, University of Minnesota Press, Minneapolis, MN. 2007.
Meyer, M.H., Ornamental Grasses for Cold Climates, University of Minnesota Press, Minneapolis, MN. 2012.
Royer, F. and Dickinson, R., Weeds of the Northern US and Canada, Lone Pine Publishing and University of Alberta Press, Edmonton, Alberta. 1999.
Kowalchik, C., Rodale’s Illustrated Encyclopedia of Herbs, Rodale Press, Emmaus, PA. 2000.
Sibley, D. A., The Sibley Guide to Trees, Random House Publishing, New York, NY. 2009.
Smith, W., Orchids of Minnesota, Minnesota Department of Natural Resources. 1993.
Smith, W., Trees & Shrubs of Minnesota, University of Minnesota Press. 2008.
Tallamy, Douglas W., Bringing Nature Home: How You Can Sustain Wildlife with Native Plants. Timber Press, Portland, OR. 2009.
Tepe, E., The Edible Landscape, Voyageur Press, Minneapolis, MN. 2012.
The Xerces Society for Insect Conservation, Pollinator Plants – Great Lakes Region.
http://www.xerces.org/wp-content/uploads/2014/03/GreatLakesPlantList_web.pdf
Vance, F.R. et. al, Wildflowers of the Northern Plains, University of Minnesota Press, Minneapolis, MN. 1984.
Watson, Ben, “Hybrid or Open Pollinated”, National Gardening Association.
http://www.garden.org/subchannels/care/seeds?q=show&id=293&page=1
White, J., Taylor’s Guides to Orchids, Taylor’s Gardening Guides, 1996.