Lesson 4. Weed Control in Pastures

Canada thistle, Cirsium arvense. Photo by Jennifer Cote.

Weed control in pastures can be a very difficult challenge. This is especially true in certain cases where animal species select against specific weed species (example: horses — tansy; cows — goldenrod, thistles, and milkweed). This is a common occurrence in all livestock grazing systems.

Plant species are unique in livestock grazing systems as compared to row crops. It is important to remember there are several plant species that are considered weeds in a row crop operation, but possess characteristics that are beneficial in a grazing system. Some of these include quackgrass, lambsquarter, and others. These plants, if properly managed can take abuse, yet still produce high quality, palatable forage. Therefore, we should focus on the plants that animals avoid eating and those containing low nutritional value such as thistles and goldenrod.

It is important to begin by scouting pastures to identify all pre-existing problems. References, such “Weeds of the Northeast” (see Appendix A), can help you identify noxious and poisonous plants. Problem areas, “hot spots,” tend to be found where animals congregate (under trees and around water tanks, etc.) or where animals tend not to graze (rock piles, steep slopes, along fence lines, etc.). This will then, in turn, help you in developing a plan to eliminate weed problems and keep from developing new ones. Your local UMaine Extension educator can help with this process.

Table 1. Maine Problem Weed List

Common Name Genus and species
Bracken Fern Pteridium aquilinum
Burdock, Common Arctium minus
Buttercup Ranunculus bulbosus L.
Cherry, Common Chokecherry Prunus virginiana
Dogbane Apocynum cannabinum
Ivy, poison Toxicodendron radicans
Loosestrife, purple Lythrum salicaria, virgatum, or any combination
Milkweed Asclepias syriaca
Spurge, leafy Euphorbia esula
Bedstraw, smooth Galium mullugo L.
Sowthistle, perennial Sonchus arvensis
Thistle, bull Cirsium vulgare (biennial)
Thistle, Canada Cirsium arvense (perennial)

Lesson 4 (continued)

Click on the links below to finish Lesson 4: