The BLM defines "noxious weed" as “any plant growing where it is not wanted. Legally, a noxious weed is any plant designated by a federal, state or county government as injurious to public health, agriculture, recreation, wildlife or property. A noxious weed is also commonly defined as a plant that grows out of place and is ‘competitive, persistent, and pernicious’.” The agency’s primary focus is “providing adequate capability to detect and treat smaller weed infestations in high-risk areas before they have a chance to spread.” Noxious weed control would be based on a program of "....prevention, early detection, and rapid response" (BLM 2013).

Animal and plant species designated as "pests" are generally species that are injurious to agricultural and nursery interests or vectors of diseases, which may be transmissible and injurious to humans.

An "invasive species" is defined as a species that is nonnative to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health (EO 13112). Invasive, nonnative species are species that are highly competitive, highly aggressive, and spread easily. They include plants designated as "noxious" and animals designated as "pests" by federal or state law.

The Nevada Department of Agriculture maintains a Nevada Noxious Weed List which was used as a reference to identify the types of noxious weeds to identify during field surveys.

During a June 2011 field survey, hoary cress (Cardaria draba), included on the Nevada Noxious Weed List, was observed in the riparian area along Twentyone Creek (as spelled on topographic maps).

The following invasive, nonnative species were observed during the June 2011 field survey: bull thistle (Cirsium vulgare); crossflower (Chorispora tenella); clasping pepperweed (Lepidium perfoliatum); bulbous bluegrass (Poa bulbosa); curveseed butterwort (Ceratocephala testiculata); Russian thistle (Salsola tragus); dandelion (Taraxacum officinale); and cheatgrass (Bromus tectorum). These invasive, nonnative species were primarily observed in previously disturbed areas intermixed with native species. No large populations or monocultures of most of these species were noted in the survey area; however, there were large populations of cheatgrass found within the previously burned areas.