The intent of noxious weed laws is to protect landowners from having their land invaded by weeds growing on adjacent land, and to reduce the likelihood of introduction and spread of new weeds. Iowa's noxious weed law is Chapter 317 of the Iowa Code. The law gives each county the authority to order the destruction of weeds classified as noxious by the state. If the owner of the land fails to address the weed problem, the county can assess the owner a fine, and if needed, control the weeds and charge the landowner for the costs of control. Noxious weeds are classified as primary or secondary, but this status only applies to the Iowa Seed Law. The Seed Law defines how many weed seeds can be present in certified crop seed. Palmer amaranth was recently added to the list of primary noxious weeds, taking effect on July 1, 2017. Counties have the authority to declare additional weeds as noxious within their borders.
| Primary Noxious Weeds | Secondary Noxious |
| quackgrass (Elymus repens) | velvetleaf, butterprint (Abutilon theophrasti) |
| perennial sowthistle (Sonchus arvensis) | common_cocklebur (Xanthium strumarium) |
| Canada_thistle (Cirsium arvense)1 | wild mustard (Sinapis arvensis) |
| bull_thistle (Cirsium vulgare)1 | wild_carrot (Daucus carota) |
| field_bindweed (Convolvulus arvensis) | buckhorn_plantain (Plantago lanceolata) |
| horsenettle (Solanum carolinense) | sheep sorrel (Rumex acetosella) |
| leafy_spurge (Euphorbia esula) | curly_dock (Rumex crispus) |
| perennial pepper-grass, hoary cress (Cardaria draba) | smooth dock (Rumex altissimus) |
| Russian knapweed (Acroptilon repens) | poison_hemlock (Conium maculatum) |
| common_buckthorn (Rhamnus spp., not to include Rhamnus alnus) | multiflora_rose2 (Rosa multiflora) |
| Palmer amaranth (Amaranthus palmeri) | common_sunflower (wild strain of Helianthus annuus) |
| puncturevine (Tribulus terrestris) | |
| teasel (Dipsacus spp.) | |
| shattercane3 (Sorghum bicolor) |
1All members of the Cirsium and Carduus genus are classified as noxious in Iowa.
2The multiflora rose (Rosa multiflora) shall not be considered a secondary noxious weed when cultivated for or used as understock for cultivated roses or as ornamental shrubs in gardens, or in any county whose board of supervisors has by resolution declared it not to be a noxious weed.
3Shattercane is the same species as grain and forage sorghum. Cultivated forms are not considered noxious.
In addition to the noxious weed, there is an additional classification of Prohibited Plants. It is illegal to import, sell, or distribute any part of these plants in Iowa. Some species are listed both as a noxious and prohibited plant.
Prohibited Plants
Teasel (Dipsacus spp.)
Multiflora rose (Rosa multiflora)
Purple loosestrife (Lythrum salicaria)
Purple loosestrife (Lythrum virgatum)
Garlic mustard (Alliaria petiolata)
Oriental bittersweet (Celastrus orbiculatus)
Japanese knotweed (Fallopia japonica)
Japanese hop (Humulus japonicus)