Thanks, friend! Cacti certainly is one correct spelling of the pluralized word for cactus. But just like if you stick a tomAYto seed in germinating conditions and it may grow a tomAHto, some cactuses are JUST as pokey as other cacti.
Given the hodge podge of a language English is (not to mention the influence of many Christmas celebrating botanical communities, I tend to find the pronunciation rule is actually a hold over and there is, in fact, NOT a proper pluralization between the two. In my experience, if it's pokey, don't poke it and if it carries two nearly identical monikers of which both are actually correct, it's just fine to happily trapse along without "correction"; even when that "correction" is couched in the ever so slightly veiled condescension that tends to follow "btw" with zero explanation, foundational grounds for the author's spelling bee superiority, authority supporting the assertion's soundness in principles of linguistics, etymology, or botanical nomenclature.
I do apologize for any excoriating tone whatsoever in this comment of mine; I simply have found over time that some folks can fall into the nasty and insulting habit of calling people out by harshly correcting the misses we all make instead of providing the unmatchable kindness of a well wrought, adequately researched topic of discussion to introduce.
I guess you could say Make Garden Org a pleasant forum again, because the off hand, passive, or sometimes even directly rude in a manner that discourages bussing plant friends.
But that's just me and I hardly know anything. Well, except the trouble with very hot steam, fairly low light, my ruby necklace melting into conditioner. And my realization I need another. Stetson out there.