Here is a beautiful couple of cacti… cactus.. cactuses?
I checked and they are all correct. You learn something new every day
“Cacti is the Latin plural of cactus, and some writers use it in English. Cactuses is the English plural. Dictionaries list both, and neither is right or wrong. Also, like many names of plants, the uninflected cactus is sometimes treated as plural.” – http://grammarist.com/usage/cacti-cactuses/