Why Should You Apply Crabgrass Preventer – An Appropriate Guide


Crabgrass prevention is a prior-emergent herbicide to be laid down before a light rain shower. The water helps the soil absorb the chemicals in crabgrass prevention. Crabgrass is a ubiquitous annual weed in the United States that quickly spreads throughout your lawn. This is why it’s vital to know which properties are most at risk from this species of invasiveness and when you should apply a crabgrass preventer. Find out more about the crabgrass preventer and the best way to apply it to your lawn.

What is a crabgrass preventer

Crabgrass preventer is one type of herbicide that targets the crabgrass weed. It is known as a preventer because it is a prior-emergent herbicide. A pre-emergent herbicide prevents the growth of weeds, but they aren’t effective in killing the weeds after they sprout. That is why the timing is crucial when you apply a crabgrass preventer. Crabgrass preventer is usually with Granules. They must dissolve the soil to ensure they can be spread across the soil and kill all crabgrass seeds and seedlings.

When should you apply crabgrass preventer

Homeowners frequently ask if crabgrass preventers lay in place before or after rain, but there is a more crucial factor in determining the temperature when to use crabgrass. The ideal temperature for soil for crabgrass is 57degF – 64degF. The seeds will begin to sprout when the soil reaches this temperature. This is why crabgrass preventers must apply before the ground is at 57 degrees, approximately 55degF. In many states, this happens in the early spring. However, this varies depending on the location. The other significant aspect is the soil’s moisture.

When the soil temperature is approaching 55degF, you need to aware of the weather forecast and when it’s likely to rain. The soil must be damp to dissolve and absorb the crabgrass preservative, so lay down the crabgrass preventer before the rainy day. When the conditions are expected to be dry, even though the soil is at the proper temperature, your lawn needs to keep moist in different ways.

You can provide adequate irrigation or regularly switch on the sprinkler during the days following the application of crabgrass herbicide. Avoid applying crabgrass preventer following rain. If you apply pre-emergent herbicide to damp grass, the herbicide will likely stick to the stems rather than absorb into the soil.

Crabgrass preventer schedule for cool-season lawns

  • The early spring (early April) is not the best time to apply Nitrogen, mainly when you have spread a Winter fertilizer before the year using Prodiamine0-0-7.
  • Dimension has some post-emergent qualities and is an anti-grow grass post-emergent specifically on younger crabgrass during the initial 1-2 tiller stages.
  • A combination fertilizer(21 per cent nitrogen and pre-emergent) is the ideal time to fertilize your lawn.
  • The 10 per cent Potassium will help ease the stress of the hotter summer months.

The above table provides an excellent crabgrass prevention plan for those seeking to manage Poa annua (annual bluegrass) and not overseeding in the fall. These pre-emergent herbicides against crabgrass affect not only the specific weeds but also the seed germination process of your healthy grass. Therefore, you should not use any of these weed killers during seeding or overseeding. A different option to replace Prodimaine in the summer months (late early September/early August) is to use Pendulum 2G with a dosage of 0.5 1 lb. per 1,000 square feet.

Soil temperatures

The most crucial factor in stopping the crabgrass seeds from sprouting is to control the temperature of the soil. The soil’s temperature (not the outside air temps (not the outside temperatures) will determine when the crabgrass seeds germinate. The initial soil temperature test occurs when soil is at or above 55 degrees Fahrenheit. Another is the temperature of the soil range of 65-70 degrees Fahrenheit. The temperature ranges for ground temperatures could last for a period of three to four months.

A crabgrass seed may be located in the soil close to the driveway or sidewalk in areas where the soil heats up faster and the seed begins to germinate earlier. While another seed of crabgrass could be located in an area that is shaded and will not get warm and grow until later. This is why we use a split application crabgrass preventer to get rid of the growth of crabgrass.

Crabgrass preventers

The most commonly used and efficient crabgrass pre-emergent herbicides include Prodiamine (Barricade), Dithiopyr (Dimension) and Pendimethalin (Halts). In this post, we’ll keep focusing on the most popular group 3 herbicides. Prodiamine and Dithiopyr. Both crabgrass preventers are regarded as root and shoot inhibitors. A vapour barrier is created within the soil layer, stopping the weeds from growing and preventing the root system from growing. The roots that aren’t developed can’t soak the nutrients or water they need, which is why they die.

It is important to note that these herbicides before the emergence of spring do not hinder the crabgrass seeds from germinating but instead block the growth of cells in the root zone and hinder the seedlings of crabgrass from growing and forming. They are also known as root pruning herbicides or root clubbers.

Prodiamine Vs. Dithipoyr

Prodiamine generally is less costly than Dithiopyrn (Dimension) Dithiopyrn (Dimension) lasts longer and can withstand excessive rain and irrigation. Prodiamine is best applied earlier in the season. Dimension later in the season. A different well-known artificial insecticide is Mesotrione. The most known Mesotrione item is Tenacity herbicide and the more generic Meso 4SC. Scott’s Starter Fertilizer which includes weed preventer also has Mesotrione. If you’re seeding in spring, use one of these pre-emergent herbicides since it’s the only product that can apply as a pre-emergent without hindering the germination of your healthy grass. It can last for about 30 days. If you’re not seeding, you can stick to the first three options because you’ll get more excellent coverage and efficacy.

Crabgrass lifecycle

Crabgrass seeds begin to sprout in the spring when temperatures in the soil reach 55°F for two consecutive days. As we’ve previously discussed, the germination period may last from the beginning of spring through summer when temperatures are at their highest. The crabgrass doesn’t thrive in complete shade but thrives in heat and sun during summer. The grassy weed prefers open spaces – therefore, any empty spots on your lawn could soon fill with crabgrass. It sheds hundreds of seeds and, if it is not prevented, spreads quickly every year.

It can rapidly outgrow and eat away at your beautiful grass, stripping it of sunlight, water, and nutrients. Then completely take over your lawn. The crabgrass dies during the season, but the crabgrass seeds stay in the soil throughout the winter months and begin the germination process and growth cycle in the spring and summer.

Crabgrass identification

The crabgrass (large crabgrass and smooth) is an annual grassy weed. They are distinct from broadleaf weeds as well as perennial and biennial weeds. The earlier and later stages of crabgrass can be light green and darken as it matures. Some species of crabgrass may develop a purple hue. The grass blades of crabgrass feature a pointed spade tip and may have white fuzz. As it grows and begins to grow into seed. As the roots develop to be four, there will be four seed heads in the collection, like fans.

Crabgrass may be confused with other grasses or weeds, especially if you have a patchy lawn with clumps of high fescue, creeping bentgrass, poa trivialis, etc. Crabgrass develops from a central vine that branches outwards from its centre. It is at a lower level, parallel to the ground, in the shape of a star, and starts to adopt an appearance reminiscent of claws when it develops (hence the name “crabgrass”).


Crabgrass preventer is a reliable method to stop crabgrass growth on your lawn. But, as it is a pre-emergent herbicide, it should apply before crabgrass has the chance of germinating. Many people recommend applying crabgrass preventer in the early spring, as this is when soil temperatures begin to rise to the temperature crabgrass needs to flourish. The ideal temperature for the growth of crabgrass is 57degF to 65degF.

The perfect time to put down crabgrass is when the soil temperature is at 55 degrees F. Crabgrass preventer must apply before the rain shower to help the soil dissolve better and absorb the chemical. Don’t apply crabgrass herbicide pre-emergent when the grass is damp from the water, as this can cause the granules to remain on the plant and not sink into the soil.

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