Lady Bird Johnson Wildflower Center – Lots of information on wildflowers and other native plants of Texas, the Lost Pines, and North America. Also a great place to visit in person!
Wildflower Center Native Plant Database – Maintained by the Lady Bird Johnson Wildflower Center. Search by common or scientific name, plant families, distribution and plant habit. Contains information about bloom season and color, soil and exposure preferences; links to the PLANTS database, wildlife value, seed sources, propagation, etc.
USDA Plants Database – The PLANTS Database provides standardized information about the vascular plants, mosses, liverworts, hornworts, and lichens of the U.S. and its territories. It includes names, plant symbols, checklists, distributional data, species abstracts, characteristics, images, plant links, references, crop information, and automated tools. This is a great resource for taxonamy, identification, and propagation.
Shinners and Mahler’s Illustrated Flora of North Central Texas – Keys, descriptions and illustrations of 2,200 Texas plants. Authoritative on-line version of the massive book.
This is a collaborative resource developed by Texas A&M University Herbaria, University of Texas Herbaria, Botanical Research Institute of Texas and numerous other universities and herbaria. They have incredible databases of vascular plants of Texas. For example, the Herbarium Specimen Browser has lists of specimens in the collections of herbaria around the state. The list can be searched by county, herbarium and plant family. State maps and lists indicate where specimens of each species have been collected, who collected it and when it was collected. This site also has a complete checklist of Vascular Plants Endemic to Texas, which also shows range maps within the state and information on whether a species is threatened or endangered.
Vascular Plant Image Gallery – Texas A&M University Bioinformatics Working Group, plant photos, arranged by family, searchable.
Image Archive of Central Texas Plants – Part of the UT Austin class, Bio406D-Native Plants of Central Texas, this site has some wonderful plant images and comments for almost 500 species to help in identification.
Native Plant Society of Texas – promoting the conservation, research and utilization of native plants and plant habitats of Texas. In addition to good information about native plants, this site has contact information for local chapters around the state.