Terry M., Regeneration of Lophophora williamsii (Cactaceae) following mummification of its crown by natural freezing events, and some observations on multiple stem formation, Phytologia, 2011, 93(3):330-340
A case description of a single plant moved to a greenhouse after freezing injury in western Texas in February 2011. The paper documents regrowth from the underground stem and distinguishes branches sharing roots from a cluster of independent plants. It also discusses different routes to the formation of such clusters. Temperatures near the population were estimated from station data. The paper does not establish a frost-hardiness threshold for the species.