When Is It Too Late To Spray For Weeds

You can fight weeds as a homeowner, yet every year, these obnoxious plants end up where you don’t want them in your yard. When you have many weeds, one of the first solutions is to reach for the weed killer.

It may appear a simple task, yet, it isn’t as straightforward as it appears. For example, many people find it troublesome to control weeds because they don’t use weed killers properly. The effectiveness of nearly any weed killer is linked to external factors. This includes the weather, the plant’s lifecycle, the season, or the weed you’re trying to kill.

You can quickly answer any questions, yet people struggle to find the answer to “when to spray lawn for weeds,” or when is it too late to spray? In our guide, you can find more about spraying weeds in your garden. By the end, you’ll see the right time to spray and the times you shouldn’t spray weed killer, such as in extremely cold temperatures. (Learn When To Water After Applying Weed And Feed)

lawn weeds

What Is The Best Time of Year to Spray for Weeds?

The best time to spray for weeds is in the spring before they grow. You can spray in the fall if you miss that weed control window.

Spring can be the best as they haven’t developed, yet in the fall, they are weaker, so your efforts can still have lots of effectiveness.

Spring is an effective time as the mild weather allows you to catch weeds before they grow, and the soil warms, allowing the herbicide to seep into the soil rather than sitting on the frozen surface.

If you can’t spray weeds in the spring or fall, you won’t be so successful in the summer.

Besides this, you spray in the winter, but you won’t find it very effective.

When are Conditions Best to Apply Weed Killer?

Remember that weather offers varying external conditions, regardless of season, which might alter weed killer efficacy. Therefore, after discussing the seasons, let us now discuss the conditions.

First, you want the soil moist but not soggy. Don’t use weed killer if it’s raining as the water dilutes it. Apply weed killer only when conditions are dry.

Apply the weed killer during calm weather as a windy day will blow your weed killer into locations you don’t want it.

Mild weather is ideal as you can’t use it in too hot or too cold weather. But on the other hand, too much heat and dryness slow the herbicide’s progress.

Cold weather isn’t ideal for applying weed killer. While it isn’t that the herbicide doesn’t reach the plant, the plant breaks down the weed killer like it was food.

Control Lawn Weeds with a Pre-Emergent Herbicide

Pre-emergent weed killers control annual lawn weeds as they sprout, which means the herbicide must be applied to the lawn before the seeds germinate. Annual plants live for one season, then produce seed and die.

Crabgrass (Digitaria Haller) and goosegrass (Eleusine indica) are annual summer weeds that germinate in the spring and winter.

In the early fall, annual weeds such as common chickweed (Stellaria media) and henbit (Lamium amplexicaule) sprout.

As a result, apply a pre-emergent weed killer in early spring to control annual summer weeds and a pre-emergent herbicide in early fall to control annual winter weeds.

Applying a pre-emergent herbicide is too late if annual weeds are already visible on your lawn.

Best Time to Apply Post-Emergent Weed Killer

When the weeds are actively growing, post-emergent weed killers are most effective. For example, selective post-emergent herbicides kill perennial broadleaf weeds like dandelion (Taraxacum officinale) and plantain (Plantago major) as well as annual weeds, but they don’t impact turfgrass.

Perennial weeds come back year after year. Therefore, early fall and spring are the optimum times to apply a post-emergent weed killer to control perennial broadleaf weeds.

Apply the weed killer on a calm day with a temperature of 60 to 80 degrees Fahrenheit and no rain expected for the next 48 hours.

weeds for spray

Granular and Liquid Weed Killers

Unless the weed killer is selective, apply weed killer evenly over the entire lawn. When using weed killers, read the package and follow the guidelines.

Regular weed herbicides destroy most plants, including turfgrass. Instead, apply a non-selective weed killer on individual weeds or patches of weeds. The most common kind of selective weed killer is granules.

Apply granular weed killer with a rotary or drop spreader for an equal distribution of weed spread.

Mix weed killer powder with water according to the label’s dilution rate and sprinkle the lawn evenly.

Agitate the spray tank regularly to keep suspended particles from sinking. Then, apply a liquid weed killer evenly using compressed air or a hose-end sprayer.

Pre- and Post-Emergence Weed killers

We can start applying weed killers to disrupt the weed life cycle on an established lawn, especially for summer weeds. Benefin and dithiopyr are two types of pre-emergence herbicides.

Spraying weed killer is best done before the weeds germinate, generally in the early spring. Then, eight weeks after the first spraying, we can reapply the weed killer.

We can use glyphosate as a post-emergence herbicide to destroy weeds. When used on immature weeds, glyphosate-based pesticides produce the best results to kill weeds by absorbing them into the plant tissue.  (Find the Best Weed Killer With Pre Emergent)

snow on weeds

Do Cold Conditions Affect Weed Killer?

Some people question if it’s too late to control weeds, especially perennials, as the weather gets colder.

However, if the plants are green and appear healthy, herbicides can be helpful in the fall. Apply herbicides when the daytime temperatures are over 50°F and nighttime temperatures are above 40°F for the days of application, thus offering optimal results. Likewise, herbicides shouldn’t be used immediately following a frost.

In the case of regrowth of quackgrass and Canada thistle following harvest, if the weeds are taller than 8 inches, glyphosate may provide effective control of both above and below ground plant components.

These plants may perish if nighttime temperatures dip below 28°F for over 4 hours, and an herbicide application may not be effective.

Quackgrass is more resistant to cold than Canada’s thistle. However, an herbicide treatment may still be beneficial if warm temperatures of over 65°F return for several days and plants appear to be growing.

The best time for dealing with the control of dandelions is during the fall, whereas the best time to control winter annuals is in the fall and early spring.

For most winter annual weeds and dandelion control in fallow fields, a combination of glyphosate and 2,4-D ester is successful.

Many winter annual weeds can be controlled with 2,4-D alone; however, it isn’t the best condition to control chickweed and is less effective on dandelion than when used in a tank mixture with other herbicides.

Rarely one weed killer spray will completely eradicate a weed. However, it would help if you went through a treatment cycle.

A weed treatment cycle is how often you must use weed killer to eradicate weeds, so they have no chance to survive successfully.

Pre-emergent and post-emergent treatment cycles exist.

Pre-emergent weed herbicides eliminate weeds before they germinate and spread, whereas post-emergent weed killers kill weeds instantly. (Learn What To Put Under Rocks To Prevent Weeds)

And, a single weed treatment is unlikely to be sufficient. Instead, you’ll need to treat the weeds several times year-round until next spring, when weeds set seed and the cycle starts again.

These weed killers contain pesticides, which may be carcinogenic and disrupt hormones. In addition, spraying weed killers many times to finish a treatment cycle may harm your health and the health of neighboring vegetation.

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