Ask Mr. Smarty Plants

You are correct that the Texas Department of Transportation (TxDOT) is responsible for seeding and maintaining wildflowers along the Texas Highways. From a previous Mr. Smarty Plants answer:

"The responsible agency on roadside plants such as this is the Texas Department of Transportation (TxDot). Here are their Vegetation Management Guidelines."

This agency has a website on Wildflowers that will give you some information, and even has a hotline phone number. Whoever answers the phone probably can't answer your specific questions, but might be able to refer you to a website or some other material that could help.

So, from our own resources, let's see what we can tell you. If you go to our Native Plant Database and search on "Castilleja" (the genus for paintbrush), you will get 54 possibilities. You can follow any or all of the plant links to get more information. We have chosen Castilleja indivisa (Entireleaf indian paintbrush), Castilleja coccinea (Scarlet paintbrush) and Castilleja lutescens (Stiff yellow indian paintbrush) as examples of the many different species of Castilleja. You probably already know that the paintbrush is hemiparasitic, requiring access to a plant, such as bluebonnets or grasses, from which it can extract nitrogen.

We understand that TxDot started doing these roadside plantings in about 1917, before the computer or the Lady Bird Johnson Wildflower Center came into being. Possibly someone was making pencilled notes of what was planted where, and possibly not. Ditto on whether those notes survived or were transcribed to more permanent records. We don't know, but we hope you can get the information you need.

We also can't tell you how far west Castilleja indivisa (Entireleaf indian paintbrush) has been seeded, but you can go to the bottom of the page on any plant in our Database, and clink on the link to USDA Plant Profiles for that plant and get a map of where it is known to grow. Following that route to the Plant Profile map for indivisa, we see that it grows from East Texas to a line  pretty well straight down through Central Texas, and one lonely county (Gaines) in the Panhandle.