Ask Mr. Smarty Plants

Pull them out. Sorry, that's the only option. Anything you spray on the weeds will kill the bluebonnets and other plants in the neighborhood. Here is an answer to the question "Is there a way to weed my yard with weed killer and not harm my bluebonnets?" which came to Mr. Smarty Plants a few days ago.

"No. There are herbicides out there for broad-leaf plants or dicots (which includes  bluebonnets), for monocots, or grasses and the broad spectrum, kill-everything herbicides that will melt your sidewalk. Many of your weeds will probably be native grasses, but spraying with a spray for monocots just threatens other monocots, like your lawn grass. Spraying with an herbicide for dicots will kill the broad leaf plants and the bluebonnets, and can also drift around to kill a shrub or two, because they are also dicots. And, finally, all herbicides and pesticides can become residual runoff material, as rain or watering causes them to run off into our water supply and subsequently into your water glass. Identify the plants you want to keep, monocot or dicot, and pull out the others that you consider weeds. Getting them out before they have a chance to go to seed will help, although the wind and helpful birds will continue to provide you with fresh stock."