Ask Mr. Smarty Plants

You are in a position to make a statement in the botanic world. We found many references to an "occasional, very rare" white flowering Sophora secundiflora (Texasmountain laurel) appearing. We even found one seed mix of 5 seeds, which inferred but did not promise a white flowering seed in that mix. We wouldn't count on that. Please follow the plant link above and particularly pay attention to the very thorough instructions under Propagation. We could find no indication that the white-flowered mountain laurel was a product of some kind of cross-breeding, which would not probably  breed true to reproduce a white flower. So, we can make no yes or no guarantees, and since you say you are going to do it anyway, you should let the Lady Bird Johnson Wildflower Center know about it, complete with pictures. This particular member of the Mr. Smarty Plants team may be no longer here, but we will be excited to hear about it none the less. Be sure and document what you do as the plant progresses.

We found 3 pictures of white-flowering mountain laurels in our Image Gallery, but no information if they were mutants of a purple flowered one or a truly different colored flower.