weeds that grow in hay fields

Herbicides can be a useful tool for weed management in pastures and hayfields. They should be used where appropriate and when cost effective. A program that integrates several different control strategies is generally more successful than relying on only one method. Weeds present at the time of herbicide application may be controlled, but if the forage stand is not vigorous and actively growing, new weed seedlings will soon emerge and occupy the bare areas that remain. Thus, without proper use of mechanical control methods and good cultural practices, herbicide use will not be beneficial.

The first step in effective weed control is to evaluate the pasture or hay field to determine the source of the weed problem. Soil testing to determine the current nutrient and pH status is the place to begin. After correcting fertility levels, the following things must be evaluated and corrected: • Stocking rate to eliminate overgrazing problems • Pasture rotation schedule • Need for additional grazing land • Prevent scalping and mowing-too-low • Correct the mower height in order to leave adequate stubble • Consider renovation where forage stands are very weak.

Grazing can be used as an effective weed management tool. Livestock will graze weeds when they are small. In the early vegetative stage of growth, many weeds have nutritive values equal to or greater than the desired forages. However, the forage quality of weeds decline rapidly as the plants mature.

When using any herbicide, it is important to be aware of the surrounding crops. Drift from many of these herbicides are lethal to other crops like vegetables, shrubs and flowers. Pesticide spray drift is the movement of pesticide dust or droplets through the air at the time of application or soon after, to any site other than the area intended. They should choose a product that will not harm surrounding crops if drift occurs. Drift will vary with boom height, nozzle type, pressure, and wind.

Mowing is especially effective in reducing the amount of weed seed produced by established broadleaf weeds. The mower should cut as close to the ground as possible. Mowing may not completely eliminate weed seed production, since some seed could be produced by plants that regrow from tillers present on grasses below the height of cutting. Also, perennial weeds that spread by underground rootstocks, like thistle, are not effectively controlled by a single mowing.

Two popular types of weed control products are pre-emerge and post-emerge herbicides. Pre-emerge herbicide must be applied before the weed seeds germinate. An example of a pre-emerge product is Prowl H2O. This herbicide is used to control Crabgrass in Bermudagrass hayfields. Post-emerge products are used to kill weeds after they have germinated. These herbicides must be used when the plant is actively growing and not simply green.

First, a weed is defined as any plant growing where you don’t want it. Therefore, we must begin to think in a broader sense as to what weeds are. A weed can be Bahiagrass or Crabgrass growing in a Bermudagrass hayfield. These unwanted plants are often more aggressive than existing or desired forage species and compete for light, water, and nutrients. In latter stages of maturity, weeds can also reduce the quality and palatability of the forage available for livestock grazing. However, not all weedy plants are detrimental to pastures. In fact, some weedy plants provide nutritional value to grazing animals.

Another control method includes various herbicides that are available to provide broad-spectrum weed control. When making your selection try to choose a product that will control as many weeds as possible. This reduces the use of herbicides and also minimizes cost by reducing the number of passes through the field. When applying multiple products choose products that can be mixed in the same tank and applied in one pass.

Weeds can reduce the quantity and the stand life of desirable forage plants in pastures and hayfields. Weeds also impact the aesthetic value of a pasture. Therefore, producers may choose to initiate weed management strategies that reduce the impact of weeds on forage production.

Most herbicides have grazing and feeding restrictions stated on the label that limit the use of the crop for livestock feed. Producers should know and adhere to any grazing or haying restrictions. These restrictions can be anywhere from seven days to one year. Different products vary in their restriction guidelines. Many products that have no grazing restrictions for beef cattle will have grazing restrictions for dairy cattle. Most will also have a withdrawal period before slaughter.

Get more information on a wide variety of forage management issues on the Georgia Forages website.

Chicory is a commonly occurring plant in all types of pastures and rough turfs across North America. It is relatively easy to control with several herbicides. Mowing in pastures might reduce flower formation but is generally ineffective in killing the plant. Hoeing or digging the taproot is successful and should be done before the seed heads form. | Photo: Wikimedia Commons.

Star-of-Bethlehem grows in the eastern half of the United States and the Pacific Northwest. It grows in pastures, landscape beds, gardens, fields, and roadsides. The plant contains cardiotoxins and glycosides that are toxic to horses; the bulbs and flowers contain the highest amounts. Few pasture herbicides are effective on mature plants. Remove small patches by hand, digging the bulbs. | Photo: Wikimedia Commons.

Scientific name: Apocynum cannabinum L. Life cycle: Perennial Poisonous: Yes.

Common Milkweed.

Bush honeysuckle describes several species of woody honeysuckles found in the eastern United States. All grow rapidly and produce multiple stems and can reach heights of about 30 feet. Large bush honeysuckle plants are difficult to remove by hand due to an extensive root system. Herbicidal control is effective. | Photo: Wikimedia Commons.

Poison hemlock is distributed across the United States and grows most frequently along fence borders in shady and moist areas. This plant is extremely poisonous to horses and humans. All plant parts contain the poisonous alkaloids; however, the fruits contain the greatest concentration of the alkaloids. Poison hemlock control is relatively easy with herbicides. | Photo: Wikimedia Commons.

Nimblewill is a warm season perennial grass that is widespread across the eastern United States. A commonly occurring plant in many pastures and turf types, it is found especially in Kentucky bluegrass fields. Mowing is ineffective to control it. Currently no herbicide is available that will control the nimblewill and not cause severe damage to desirable pasture grasses. | Photo: Wikimedia Commons.

Hemp dogbane grows throughout North America. It’s poisonous to horses, with the leaves toxic at all times, including dried in hay. The toxic substance is a glycoside that can cause digestive disturbances, diarrhea, and weakness. Controlling it in pastures is difficult. Mowing is often ineffective and herbicidal treatment requires multiple applications. | Photo: Wikimedia Commons.

Common ragweed is distributed widely across the United States and occurs in pastures and cultivated crops. Infestations in pastures are usually more of a problem during periods of drought or when overgrazing occurs. Common ragweed control is relatively easy: apply herbicides to plants less than 12 inches tall that have not been mowed. | Photo: Wikimedia Commons.

Common milkweed grows throughout North America except in the extreme southern, southwestern, and far western states. It produces cardiac-glycosides that are toxic to horses and might cause depression, irregular heartbeat, diarrhea, weakness, labored breathing, and even death. Plant control is difficult. Hand weeding and removing the deep taproot might help. Mowing is generally ineffective. | Photo: Wikimedia Commons.


White snakeroot is a warm-season perennial frequently found in shaded areas of pastures near streams or woods. These plants are toxic to horses; both fresh and dried leaves contain the toxin. Cumulative intake between 1 and 10% of body weight is toxic and can be lethal. Removing these plants from the pasture by hand is often the best course of action. | Photo: Wikimedia Commons.

Learn how to identify invasive, noxious, and sometimes poisonous, pasture weeds that commonly infest horse pastures.

Tall ironweed is distributed widely across the eastern half of the United States and is found most frequently in low damp areas of pastures and roadsides. Tall ironweed control is possible when herbicides are applied to plants less than 12-15 inches tall that have not been mowed. Mowing is an effective treatment to prevent seed production. | Photo: Wikimedia Commons.

Buttercup is the common name for several Ranunculus species distributed across much of the United States. Buttercups can be poisonous to horses, but the plants are not palatable and usually not eaten by animals. Mowing is usually ineffective for controlling buttercups, however; they are easily controlled with several herbicides. | Photo: Wikimedia Commons.

Hemp Dogbane.

Spiny pigweed is distributed widely across the United States and grows most frequently along fence borders, feeding/watering areas, and other compacted areas. Control is relatively easy with herbicides applied to plants less than 12 inches tall. Mowing and hand weeding are effective if done before flower production to prevent seed formation. | Photo: Wikimedia Commons.

Buckhorn plantain is widespread across North America and is a commonly occurring plant in all types of pastures and rough turf. It readily survives overgrazing and compacted horse pastures, especially when rainfall is limited. Buckhorn plantain is relatively easy to control with several herbicides; however, mowing in pastures is generally ineffective. | Photo: Wikimedia Commons.

Wild carrot, also known as Queen Anne’s lace, is an erect biennial that can grow to about 4 feet in height. It is found in pastures, native areas, fields, and roadsides. Mild neurotoxicity to horses was reported in Europe but is not considered a serious threat in North America. Controlling wild carrot in pastures is easy using timely mowing before flowering and herbicidal treatment. | Photo: Wikimedia Commons.

Pigweed is an invasive plant pest usually found in disturbed areas, like farmland and along roadsides and fencelines. Because their aggressiveness can reduce crop yields, this PNW discusses how to prevent or curtail their spread .

Gordon Jones | Dec 2020 | OSU Extension Catalog Peer reviewed (Orange level)

Shelby Filley | Nov 2021 | Article.

Gene Pirelli | Oct 2021 | Video Peer reviewed (Gray level)

Apr 2009 | OSU Extension Catalog Peer reviewed (Orange level)

Forages – hay and pasture collection.

White campion, also known as white cockle, contaminates hay fields, roadsides, ditches, and fencerows because of its high rate of seed production and tolerance to many herbicides. This publication provides information on identification.

Tania Siemens | Dec 2012 | Featured question.

Information from OSU.

An Oregon State University-led research team responded to the problem of glyphosate-resistant Russian thistle – a weed that infests nearly 5 million acres in the Pacific Northwest, and through four years of fieldwork, developed .

Larry Lutcher, Judit Barroso | Dec 2018 | Impact story.

This is a report on a research project where the objectives were to determine whether grazing cow-calf pairs on warm season grasses and brassica pastures would extend the grazing season and positively affect calf weaning weights, feedlot performance, carcass characteristics, and ranch profitability.

Shelby Filley | Nov 2021 | Article.

Andy Hulting | Aug 2018 | OSU Extension Catalog Peer reviewed (Orange level)

Here is a collection of our favorite resources for weeds in pastures and hayground.

Orchardgrass response to grazing.

Noxious and invasive weeds.

Russian thistle thrives in the dry climate of eastern Oregon and Washington and if left unchecked develops an extensive root system that competes with wheat for water and nutrients.

Nov 2021 | OSU Extension Catalog Peer reviewed (Orange level)

Winter is approaching and it’s time to check in on your weed control plans. Noxious weeds are best controlled if you track them carefully. Weed mapping and weed calendaring are two activities important to tracking weeds so that you can properly control them. Here are a few tips to get you started.

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Tracking Noxious Weeds.

This full-color illustrated guide for optimizing alfalfa production according to the growing conditions common throughout Idaho and east of the Cascades in Oregon and Washington provides specific recommendations for all critical nutrients.

Mitigating rattail fescue has become easier: this publication addresses this increasingly common weed in Pacific Northwest cropping systems.

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Announcements on educational programs and important news & notices for western Oregon producers of beef cattle, sheep and goats, plus forages to support these livestock.

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The practice of knowing the nutrient content of feeds and matching those up with the nutrient requirements of your livestock is very important. Balancing rations can help with keeping feed costs in check with production level .