About.com: Poisonous Plants for Cats, Dogs, Humans
Article listing a number of poisonous plants, with links to further information about those plants.
All Things Plants
Gardening community centered around a jointly edited database of plant species and varieties, with forums and blogs.
BBC: Plant Finder
Plant database with a photo and horticultural description for each entry. Searchable by botanical and common names, as well as other characteristics
BackyardGardener.com: Garden Guides on Plants
Starting point for information on (types of) plants, with summary information for many species and varieties.
Cal's Plant of the Week
Features a new plant every week, with photo, description, and cultural information. Previously featured plants can be selected by botanical or common name. Focus is on plants for greenhouse culture.
Chicago Botanic Garden: Ornamental Plant Development
Provides access to plant evaluation reports from the Botanic Garden's plant trials. Each report, in PDF format, provides several pages of description and photos.
Dave's Garden: PlantFiles
Database with over 80,000 plants with cultivation information and pictures supplied by member gardeners.
Features searchable database of thousands of plants, with basic information and often photos. Includes many succulents, herbs, and tropical fruit trees.
Dinosaur Garden Plants
Describes plants that lived during the age of the dinosaurs, with brief information, lists, and links to other resources for plants of the mesozoic era.
Garden plant finder. Searchable by garden conditions and design requirements such as flower color, size and growth habit. Search results include plant photo and summary information.
Features hundreds of plant portraits, each illustrated with several photos, documenting the garden uses and cultural requirements of each species or cultivar.
Search a database of live and cut flowers according to color, usage, and other criteria. Includes photo and summary information for each plant.
Flowers of India
Collection of hundreds of plant photos with brief descriptions. Each of the plants grows in India, but both natives and non-natives are featured.
Fruits and Vegetables
Includes set of fact sheets and links from the University of Florida.
Plant database with search engine to find plant ideas according to location, design and lifestyle. Free membership gives access to online journal with folders, to-do's and notes.
Gardenweb: Name That Plant
Forum that allows users to upload images of plants that they are trying to identify.
Features a searchable, multilingual garden plant encyclopedia, with a summary of cultural and botanical information and in many cases photos.
Provides articles on selection, culture, and propagation of several popularly grown perennials and bulbs.
Illinois' Best Plants
Chicago Botanic Garden provides a database of recommended plants for Illinois gardens, from perennials to trees, with photos and information on their culture and use.
Jesse Saylor's Plants
Plant information database, including photographs, Latin name pronunciations. Searchable by botanical and common names, and plant characteristics.
Mister Smarty Plants
Plant and flower identification: users upload pictures of unknown plants. Site members identify them and score points for correct answers.
New Jersey Weed Gallery
Database of weeds, accessible by common and botanical names and by a thumbnail gallery. Summary information and photos are provided for each weed.
Pacific Northwest Plants
Database on plant identification, culture and usage for the U.S. Northwest, including native and introduced species and their major varieties and cultivars.
Gardener Mark McDonough presents horticultural musings and illustrated plant studies, with particular emphasis on alliums and other bulbs for rock gardens.
Includes information about plants native to southern Africa, including hundreds of alphabetically arranged plant portraits, by the National Botanical Institute of South Africa.
Plants For A Future
Resource centre for rare and unusual plants, particularly those which have edible, medicinal or other uses. Offers a plant database, and various articles on gardening, perennials, and habitats.
Plants National Database
Online USDA database of botanical information, images, and links on plants in the USA, including crops and invasives. Search by name, geographic distribution, or other characteristics.
Rob's Plants: PlantLinks
Directory of web pages about plants, selected for their interest to gardeners. Primarily organized by botanical classification.
Plant encyclopedia featuring photos and short descriptions of annuals, perennials, shrubs, and trees.
The Families of Flowering Plants
Offers descriptions, illustrations, and identification retrieval.
The Garden of Paghat the Ratgirl
Pacific Northwest gardener presents essays for hundreds of species growing in her garden, with personal notes, history, cultural information, and photos for each.
Translation program for botanical Latin.
Offers a weed listing for the United States regions, primarily weeds occurring in lawns.