When is The Best Time to Spray Pastures for Weeds?

Whether you have a few or many acres of pasture on your property, the wide-open space will inevitably attract plants other than the grasses that you want to keep. Certain points in each season will be better than others for effective control of your pasture’s unwanted growth. This will vary based on the kinds of weeds present, the weather, as well as your management schedule and approach.

Identify The Weeds

Before applying any herbicide, identify the weeds in your field. Not all weed control products kill all weeds, and those that do will probably also affect your grass. By identifying the plant species that you want to target, you can then choose a grass-safe product that will be the most effective herbicide for your specific weeds.

Perennials, multi-year species that have hearty root systems like woody plants and grasses, need to be dealt with differently than annual weeds that are dispersed by seeds and don’t have permanent roots.

Getting into the field and looking closely at the ground is important for good identification. Some weeds, like thistle, dandelions, or small trees, will be visible by scanning the pasture, but others like clover and grassy weeds will be covered or blend in with your pasture grass. Take a sample survey of various points across your field to get an accurate inventory of what needs to be taken care of.

Weeds in Grass

Seasonal Applications

The best time to spray herbicide will depend on the weather. Cool-season and warm-season weeds must be approached at different times of the year. The best times within these periods are just before the weeds begin to germinate (pre-emergent) or after they have sprouted and are in an active growth period (post-emergent). Generally, spraying once per year for warm-season and once per year for cool-season weeds will keep your fields clear of volunteer growth.

  • Late winter – Spraying pre-emergent herbicides in late winter will pre-empt germination of weeds and allow your grass to grow in without competition as the temperatures warm up.
  • Early spring – Post-emergent herbicide should be applied in the early spring when annual, and perennial weeds are actively growing and absorbing nutrients. Although, you should avoid spraying herbicide while your warm-season grass transitions out of dormancy.
  • Late summer – A late-summer application of pre-emergent herbicide for cool-season weeds will, like in early spring, pre-empt unwanted growth and allow your cool-season grass to grow in without competition.
  • Early Fall – Post-emergent applications in the early fall should be done at least 2 weeks before the first frost because, after that, it is too late to spray for weeds. Frost-damaged leaf tissue won’t effectively absorb the formula. However, damaging the plants before the frost will decrease the likelihood of survival through the winter.

Can You Spray Pasture For Weeds In Summer?

The beginning and middle of summer aren’t the best times to spray for weeds. They should be targeted before they show up or during their active growth phase while still young. In the case of pre-emergents, the plants don’t get a chance to grow to maturity.

A post-emergent is used while the plant is growing and absorbing nutrients most actively during adolescence. By summer, annual weeds have reached maturity and released their seeds, setting the next year up for more growth. Similarly, perennial weeds have a period of active growth in the early seasons before a period of stability that precedes dormancy.

Applying Herbicide

Drexel De-Amine 4 - Also Known as - 2, 4-D Amine Weed Killer, 128oz - Gallon

When you apply a grass-safe herbicide like 24D, Tordon, or Milestone, read the label and directions for specific instructions on using the particular product. These formulas are developed to be safe on certain grasses and target specific kinds of weeds, either before or after they emerge.

It’s required to get a license for private pesticide application to have access to restricted products, and the education helps you understand how to use the products safely and confidently.

Spray herbicide shouldn’t be applied to wet grass when there is rain in the forecast or if it is windy. If it’s wet out, the application will be diluted and may be rinsed away, and a windy day will result in uneven coverage.

Rotate Your Grazing Animals

Applying herbicide to grazing fields requires an added logistic aside from the timing, pasture spraying rates, and weather: your grazing animals. They should be kept off the treated pasture for a few days while the formula dries and is absorbed.

If you use manure from your grazing animals for fertilizer, a non-residual formula should be applied on the pasture, as opposed to a residual one. A residual herbicide is long-lasting and won’t break down quickly, so if it’s consumed, it will be redistributed as animals rotate across other fields, which may not be desirable.

How To Get Rid Of Weeds In Pasture Without Chemicals

There are three ways to manage weeds other than chemical options. These include mechanical or manual, cultural, and biological methods.

Mechanical Or Manual

Some land managers prefer mowing pasture to control weeds. This can be effective for flowering annuals as long as they are taken care of before they drop seeds. For perennials, this may keep them trimmed, but by not targeting the roots, they will regrow regularly. Large, hearty weeds like small trees and bushes may need to be pulled by hand to be cleared away effectively.


Focusing on the culture, or the growing environment, of a plant, is another method of weed control without the use of herbicide. Some weeds are a symptom of poor soil conditions for your pasture grass, like dandelion or nutsedge. When your desired grass grows in with dense coverage, there will be less space for more opportunist species to show up. Performing a soil test to check the nutrient profile and the pH will help you keep your soil fertile and foster the environment that is best for the grasses you want.


Pasture Weeds

Incorporating animals into your weed management program is a cost-effective solution that doesn’t include chemicals. Horses or cattle may be your regular grass pasture browsers, but adding goats and sheep to your field rotations will help control undesirable plants.

Goats will eat woody growth, while sheep will graze on broadleaf weeds. Certain plant species may be toxic to some animals, another way that a preliminary inspection and inventory will support the right managerial method for weeds on your property.