 invasive plants these ornamental plants may look nice growing wild but they re wreaking havoc on our environment in 1993 an estimated 4 billion was spent to control the spread of over 1400 nonnative pest plants nationwide most of this was spent killing agricultural and rangeland weeds but much of it went to fighting the 450 or so exotic pests originally brought here as ornamental garden plants from europe asia africa and australia many of these plants are still being sold in nurseries today source  fine gardening magazine   