Guevara J. C., Gonnet J. M., Estevez O. R., Frost hardiness and production of Opuntia forage clones in the Mendoza plain, Argentina, Journal of Arid Environments, 2000, 46(2):199-207, doi: 10.1006/jare.2000.0664
The field experiment compares damage to forage clones after a severe frost in 1999. It takes plant age and planting site into account.