Jerry, this is very interesting what you say about root overgrowth and the clogging of the pot. Hope you don't mind my rephrasing. I have had a L. purpurata v carnea for many years, and have never noticed this. However, I repot every year, so that all dead roots get removed every year, and the plant gets divided as soon as possible for space reasons, so I just don't have your problem. I lost this plant to the virus testing that is going on right now, but have a dozen or so seedlings in various stagges of maturity, with oldest about to bloom this year. I will keep an eye open for this pattern, but I don't remember any of these plants sending roots out in a disagreeble manor. Maybe they like my mix and choose to enter it without a fuss. Here is a picture of the one I had. Really hated to loose it. I'm hoping one of the several replacement seedlings will come out a similar color.
http://www.pbase.com/schnitz/image/57225999
Cynthia, Prescott, AZ