Ask Mr. Smarty Plants

I can guide you to a source that will produce a list of a large number of the native plants of Kerrville/Kerr County, TX; but it would be very difficult, if not impossible, to assemble a list of all the native plants that grow there.  Here is how to get a list of the native plants that have been reported as occurring in Kerr County, Texas by the USDA Plants Database: 

Go to the USDA Plants Database.  Select "Advanced Search" from the Search menu on the left side of the Home page.  On the "Advanced Search and Download" page under Part A:  PLANTS Core Data choose "Texas:Kerr" under "County Distribution" in 1.  Distribution.  In 2.  Taxonomy put a check in the "Display" box beside "National Common Name".  Next, under 3.  Ecology select "North American Native" under "Native Status" and put a check mark in the "Display" box.  Scroll down to the end of Part A (just before the beginning of Part B:  Characteristics Data) and click on the yellow box that says "Display Results".  

This will give you a list of ~570 North American native plants that have been reported as being found/collected in Kerr County. This won't be a complete list of all the native plants in Kerr County, but it is a pretty good start.  The USDA Plants Database get their data from several sources, e.g., records of specimens of the plant in internationally recognized herbariums; publicly available published literature (preferably peer-reviewed) such as scientific journals, floras, masters theses and doctoral dissertations; and verified records from interested individuals.  You can read the Standards for Contributors that must be met in order for a plant record to be added to the database.

For a shorter list of the more common wildflowers in Kerrville, you can find a Wildflower Check List on the web page of the Kerrville Chapter of the Native Plant Society of Texas.  The list includes links to photos of many of the species.

Certainly not all plants that are native to Texas are also native to the Kerrville area, but there are several sources that cover all vascular plants, both native and introduced naturalized plants, in Texas.  They are:

• Correll, Donovan and Marshall Johnston.  1979.  Manual of the Vascular Plants of Texas.  Richardson, TX:  University of Texas.  They report 4,839 species in Texas.  There are no distribution maps.
• Jones, Stanley; Joseph Wipff and Paul Montgomery.  1997.  Vascular Plants of Texas:  A Comprehensive Checklist including Synonymy, Bibliography, and Index.  Austin, TX:  University of Texas.   They report 5,812 species, with no distribution maps.
• Turner, Billie; Holly Nichols; Geoffrey Deny and Oded Doron.  2003.  Atlas of the Vascular Plants of Texas.  Volume I: Dicots.  Volume II: Monocots.  Fort Worth, TX:  Botanical Research Institute of Texas (BRIT).  There are county distribution maps for approximately 6000 species in Texas.

If you wanted to take the time and effort, you could go through the maps in the two volumes of the Atlas of Vascular Plants of Texas and note those species that occur in Kerr County.   I would imagine that there would be approximately 570 plants—perhaps a few more because the publication also includes naturalized plants.  The sources used to compile Dr. Turner's list are similar, if not identical to those used by the USDA Plants Database.