We have selected USDA Plants Database as the world's very best website on American Plants.
The USDA Plants Database website is published by the United States Department of Agriculture. It provides information, in standard format, about the vascular plants, mosses, liverworts, hornworts, and lichens on the USA and its territories. For each plant, the database provides names, plant symbols, checklists, distributional data, species abstracts, characteristics, images, crop information, automated tools, web links, and references. Overall, the website contains more than 200,000 pages.
In addition to its main plants database, the USDA Plant Database website contains sections on: Alternative Crops, Characteristics of Plants, Classification of Plants, Culturally Significant Plants, Plant Distribution Update, Fact Sheets & Plant Guides, Invasive & Noxious Weeds, Plant Materials Publications, Threatened & Endangered Plants, and Westland Indicator Status.
There is also a plant photo gallery, to which users can contribute. It holds more than 30,000 plant images. To maintain quality, contributors must provide at least 100 images, which must all be accurately identified by scientific name.
Click here for the website of the USDA Plants Database: http://plants.usda.gov