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 Noxious Weed Species to be Controlled



Listed below are weed species descriptions, distribution, problems, and possible management methods for weeds considered noxious by the State of Iowa and Johnson County. This web page is meant to give general knowledge of these problem weeds, why they are a problem, and common methods of control. Individual weed and management circumstances may vary and these recommendations should be used as changing situations dictate.

The Iowa Department of Agriculture and Land Stewardship and the Code of Iowa have declared 27 species of plants as noxious weeds which need to be controlled. The State of Iowa has declared the following weeds noxious:

    Buckhorn Plantain  (Plantago lanceolata)
Buckthorn  (Rhamnus species)
Bull Thistle  (Cirsium vulgare)
Butterprint  (Velvet-leaf) (Abutilon theophrasti)
Canada Thistle  (Cirsium arvense)
Cocklebur  (Xanthium strumarium)
Field Bindweed  (Convolvulus arvensis)
Horse Nettle  (Solanunum carolinense)
Leafy Spurge  (Euphorbia esula)
Multiflora Rose  (Rosa multiflora)
Musk Thistle  (Carduus nutans)
Perennial Peppergrass  (Hoary Cress) (Cardaria draba)
Perennial Sow Thistle  (Sonchus arvensis)
Poison Hemlock  (Conium maculatum)
Puncture Vine  (Tribulus terrestris)
Purple Loosestrife  (Lythrum salicaria)
Quackgrass  (Agropyron repens)
Red Sorrel  (Sheep Sorrel) (Rumex acetosella)
Russian Knapweed  (Centaurea repens)
Shattercane  (Sorghum bicolor)
Smooth Dock  (Rumex altissimus)
Sour Dock  (Curly Dock) (Rumex crispus)
Tall Thistle  (Cirsium altissimum)
Teasel  (Dipsacus species)
Wild Carrot  (Daucus carota)
Wild Mustard  (Brassica kaber)
Wild Sunflower  (Helianthus annuus) 

In addition to the State of Iowa Noxious Weed List, Johnson County lists an additional four species of noxious weeds. These species are:

   Japanese Knotweed (Polygonum cuspidatum)
Marijuana (Cannabis sativa)
Poison Ivy (Toxicodendron radicans)
Wild Parsnip (Pastinaca sativa) 

This web page also contains very general herbicide control methods. This web page is not intended to promote the sole use of herbicides, rather using herbicides as a tool and as an overall part of an integrated weed management program. Changes in pesticide regulations occur constantly. If you have questions about the usage or legality of certain herbicides, contact your County Extension office, or the Iowa Dept. of Agriculture & Land Stewardship. Always read and understand chemical labels before use. The recommendations for using herbicides included in this web site are incomplete and should not serve as a substitute for herbicide labels. Complete instructions for the use of a specific herbicide are on the herbicide label. The pesticide user is responsible for applying pesticides according to label directions, as well as for problems that may arise through misapplication or misuse of the pesticide. Label changes, product cancellations, and changes in recommendations may have occurred since the production of this web site. Before using herbicides, consider whether possible impacts of chemicals outweigh the benefits of other management techniques, whether there are other appropriate management choices, and also whether the area is appropriate to use herbicides. For more specific information on plant identification or management, consult with knowledgeable professionals before attempting control. Some weed species are nearly impossible to manage without the careful use of some herbicides. The best weed control program begins with prevention. Once weeds are established though, using several management methods in an integrated weed control program will generally give the best results.

A variety of methods are used to control invasive and noxious plants. Their effectiveness will vary with the type of infestation, weed species, and the skill and dedication of the persons controlling weeds. Select a control method, which meets the goals of the particular area (i.e. lawn, prairie, agricultural field, etc.) where weeds have invaded. The majority of these management methods are most effective when used in combination as part of an integrated vegetation management program. For example, much better control of canada thistle (Cirsium arvense) can be achieved using mowing, competitive seeding, herbicide applications, and prescribed burning all as management tools, rather than relying solely on just one method.

Identifying noxious weeds correctly and preventing them from establishing is a much more efficient and effective management strategy than is waiting for a weed to reach epidemic levels. With some weed species, such as canada thistle, japanese knotweed, or purple loosestrife, this may be the only real opportunity to "control" the weed. Some noxious weeds are extremely difficult to get rid of once they are established, and long-term management is necessary just to reduce their populations to acceptable levels. Noxious weed management is expensive in terms of dollars, but also in time spent and energy used.


Bullet Don’t know what a word means?

Try looking in the glossary of plant terms for help. Here you can find various explanations of terms such as "annual", or "rosette" to assist in correctly identifying characteristics of some of the noxious or invasive weeds of Johnson County.


Bullet Where can I find references on weeds?

A list of text references is available to help find materials on weeds and weed control. Local libraries, extension offices, etc. often have various information on native plants, noxious and poisonous plants, and alternative plants which can be used in landscaping or around the home. Use these materials to learn more about the native and introduced plants in Johnson County.