Pre-emergent can remain effective in your lawn for 2–6 months, depending on the type you use. During this time, it will kill all grass, weeds, and other plant seeds as they sprout. Excessive rain can reduce the effective lifespan of pre-emergent herbicides, but pre-emergent weed control products are designed to withstand regular rain and watering.
What Does Pre-Emergent Herbicide Do?
Unlike other herbicides, pre-emergent is designed to kill plants before you see them. Pre-emergent enters the soil and remains there for several months. During this time period, all seeds that germinate underground will be killed by the pre-emergent.
- Kills seeds as they attempt to sprout underground.
- Attacks all seed types, including weeds, grass, garden plants, and trees.
- Do not seed your lawn while pre-emergent is active. It will kill grass seed.
Although pre-emergent herbicide is sometimes referred to as “crabgrass preventer,” it is really a seed-sprout preventer. Make sure not to spread pre-emergent anywhere you plan to plant grass, flower, or vegetable seeds in the next few months.
What is the Longest-Lasting Pre-Emergent?
Barricade is commonly considered the longest-lasting pre-emergent on the market. It remains effective for up 6 months in the soil. If you apply Barricade in March to stop spring Crabgrass, it will prevent all spring weed seeds and summer annual weeds from sprouting.
- Barricade has the longest pre-emergent effectiveness at 6 months.
- Apply Barricade in spring to stop weeds until fall.
The 6-month window for Barricade is perfect for many yards. By applying in March, you stop spring and summer weeds. Then, by the time the pre-emergent loses its effectiveness, you can overseed your lawn with new grass in fall. If you don’t plan to overseed, you can or perform a second application of Barricade to stop winter annuals like Poa Annua (Annual Bluegrass).
Top 5 Pre-Emergents: How Long do they Last?
When considering which pre-emergent you want to use, it’s important to know their effective lifespan. This can help you select the right product and plan your lawn care schedule appropriately in case a second application is needed to stop summer or fall weeds. Here are the top pre-emergent products and their effective lifespan.
How Long Does Scotts Pre-Emergent Last?
2–4 months is the typical effective timespan of Scotts crabgrass preventer pre-emergent. Although it isn’t the longest-lasting pre-emergent on the market, Scotts combines pre-emergent controls with fertilizer to feed your lawn and stop seed germination in one step. This is more cost-effective than separate pre-emergent and fertilizer products, and repeat applications feed your lawn at the same time they stop weeds.
How Long Does Dimension Pre-Emergent Last?
Dimension pre-emergent is effective for 4 months after application. This makes Dimension a long-lasting pre-emergent. Keep in mind, when mixing and spreading Dimension that it should be diluted to product label rates. Only .55 ounces of Dimension are required per gallon of water. This solution is enough to cover 1,000 square feet of yard.
How Long Does Preen Pre-Emergent Last?
Preen prevents seeds from sprouting for 2–3 months after application. This puts it on the lower end in terms of pre-emergent lifespans. However, Preen is one of the safest pre-emergents for use in and around gardens and flowerbeds. While overapplication of some products may harm ornamentals, Preen is gentle enough to use around delicate plants.
How Long Does Gallery Pre-Emergent Last?
Gallery makes big claims, with an in-soil weed prevention lifespan of 4–8 months. The difference between these two extremes is fairly large though. How long Gallery remains effective depends largely on soil and watering conditions. Sandy soil and heavy watering can reduce the effectiveness of Gallery down to 4 months, which is still impressive, but its claims of an 8-month lifespan don’t always measure up to the known long-term power of Barricade.
With promises of seed germination control of at least 3 months, Pendulum 2G shines not because of extended effectiveness, but because it boasts superior control of invasive grasses, including crabgrass and Poa Annua. If your lawn is constantly invaded by crabgrass, apply Pendulum 2G in spring when the soil temperature rises to 55℉ (13℃). In yards afflicted with Poa Annua, apply Pendulum 2G in fall when soil temperatures dip down to 70℉ (21℃).
How Long is Pre-Emergent Effective?
Pre-emergent effectiveness windows vary by product. Pre-emergents with a short timespan last at least 2 months in the soil, while industry leaders last for 6 months, with some boasting the possibility of an 8-month lifespan. When possible, choose a long-lasting pre-emergent and apply it early, rather than late. You’ll have the best luck stopping weed seeds by spreading a powerful pre-emergent weed control early in the season and trusting it to keep your lawn weed-free for months to come.