i have been trying to find this out for a long time now, is it due to prickly stems? do they need to be planted in cactus type soil? or is it just the name?
why is the giant cactus zinnia have "cactus" in the name?
Not sure about zinnia, but in dahlias the "cactus" describes the type (form) of the flower.
The petals look like cactus spikes - at least they did to whoever named them
No you dont need special Cacti soil, the discription is usually related to either the shape of the flower as said before, the rough or spinney foliage/stems or the dry conditions they like to grow in, but Zinnias are not related to Cacti, good luck. WeeNel.