Here is a link to a similar thread.

Does your soil have caliche in it?

Common problem in the high deserts of the Southwest. I wouldn't be surprised to find it in Texas. I don't know what to do about it, but this might help you find an answer. (In central Nevada we didn't even try to cope with it. Just used raised bins for the few flowers we could afford to water.)

Thanks, bpgreen. I missed that recent post and will try some of the suggestions there.

Albert: No caliche in my immediate area (thank goodness) but I do know people around here with it.