This is generally considered to have spread into North America from subtropical or tropical regions to the south (e.g. F, W). But it may have been present early after settlement. The earliest record in Ky. comes from Short & Peter (1835). In 1914, Gm noted: "very common everywhere in Kentucky." It is the only spiny member of Caryophyllales in Ky., apart from the prickly pear (Opuntia). And like some "smartweeds" (Polygonaceae), it often has whitish "chevrons" on its leafs (pale V-shaped marks)--perhaps a warning to herbivores! See also notes under palmeri, which may be closely allied with subgenus Acnida as well as spinosus; 2n = 32 and 34 in both species (FNA 4).