Escobaria missouriensis a/k/a Missouri Foxtail Cactus, Continuing saga.
I have now located a total of about 70 Escobaria missouriensis cacti in City of Lubbock parks. They tend to occur in groups maybe 10 meters in extent. I have found five such groups, one at Mackenzie Park, and four around Dunbar Lake. The groups are all centered around caliche knolls, ridges, or banks.
I have learned to look on high relatively inaccessible and undisturbed caliche outcrops.
Undisturbed for how long? I do not know how long E. missouriensis lives. Some of the larger Escobaria are surely 50 years old or more. It is possible that the places I am finding Escobaria may never have been broken by plow or graded.
How fire resistant is Escobaria? It is possible too that the places it is found have not been burned or do not support enough grass to fuel a hot prairie fire.