most of them escape in the wild, and established wild population. iceplant is another one, its from south africa, it actually doesnt help with preventing spread of fires,it blankets the coasts of california. relatives of the plants are quite nifty succulents for hobbyist(aizocae, aka stone plants) while the ornamentals are very hard to take care off, the iceplants is very hardy and invasive. blue gum, a type of eucalyptus grows fast, also invasive but the biggest problem is since its a eucalyptus it makes fires more dangerous because of the oils.