Refuge

Lady Bird Johnson Wildflower Center

Excellent resource for North America, find Native plants by State or Province, search plant lists, Native plant distributors and find local native plant organizations near you.

Pollinator Partnership

Pollinator Partnership’s mission is to promote the health of pollinators, critical to food and ecosystems, through conservation, education, and research. They have downloadable eco-region guides and zip code based searches.

National Wildlife Federation

Although still a work in progress, NWF's beta plant finder is a great resource to find host relationships between plants and butterflies/moths.

Audubon's Native Plant Finder

Audubon's Native Plant Finder is easy to use. Its focus is on what plants will attract birds in the United States, you can search for flowers, scrubs, trees etc. Just enter your zip code and get started.

Prairie Moon Nusery

Prairie Moon Nursery has over 700 different native species profiled on their site. You can search for hardiness zones, height, light + soil requirements, boom time and color.

They sell seeds, potted and bare root plants. A one stop shop.

Grow Milkweed Plants

Everything you need for finding and learning about Milkweeds native to the Americas. You can search Canada, US or Central America by state or providence. The website now features a Milkweed Podcast too!

Prairie Nursery

Prairie Nursery's beautiful website is packed with content and resources. Their search function allows for a variety of inputs. This is another one stop shop for Native Plants and Seeds

USDA's PLANTS Database

The PLANTS Database provides standardized information about the vascular plants, mosses, liverworts, hornworts, and lichens of the U.S. and its territories. Search by state, in addition the website has a trove of information. 

Xerces Society

The Xerces Society has compiled even more resources here. Search by state for their recommend seed mixes!