Roundup is one of the best-known names in weed control.
The first iteration of Roundup was developed by Monsanto in 1974 and added glyphosate to herbicides for a remarkably effective weed killer.
Today, the famous Scotts Miracle-Gro company owns Roundup and has several formulas to handle specific needs.
But, this also means that Roundup varieties work at different rates.
Here’s everything you need to know about how fast the most popular formulas take to work.
How Long Does It Take Roundup To Work?
Each Roundup formula is slightly different, but the products will usually take 1 to 2 weeks for a root kill.
Certain conditions may delay this timeframe, such as heavy rainfalls or applying to completely dry plants.
Different Products For Different Uses Have Different Timeframes
One of the biggest mistakes people make is to assume all Roundup products are the same. Instead, each one has a formulation to perform a designated task.
There are three different categories of time to watch out for:
- Rainproofing (i.e., how long until rain no longer washes away the herbicide)
- Initial Effects (i.e., when the weeds first show signs of wilting, yellowing, or other damage)
- Root Death (i.e., when the herbicide has made its way down the plant and kills the actual root system)
Depending on the product you’re using, one or all of these timeframes may be different.
Roundup Extended Control Grass & Weed Killer Plus Weed Preventer II
This product combines glyphosate and imazapic to create a long-lasting solution for weeds.
- It becomes rainproof after about 30 minutes,
- The first signs of wilting and yellowing occur in about 3 hours,
- Root death occurs in about 1 to 2 weeks.
The herbicide remains effective for up to 4 months.
Roundup For Lawns
Because lawn grass is a domesticated weed, you have to be extra careful when treating lawns.
To provide the safest possible treatment, Roundup for Lawns uses a blend of 2,4-D, dicamba, dimethylamine salts, penoxsulam, and sulfentrazone instead of the usual glyphosate.
Water your lawn before applying, and you’ll see the first signs of the herbicide at work in as little as 30 minutes.
Several formulas work a bit differently from one another.
- Roundup for Lawns 1 for northern grass types targets 253 different types of common weeds and becomes rainproof in about 3 hours. It remains effective for up to 3 months.
- Roundup for Lawns 3 is a slightly different formula with the same effects as Roundup for Lawns₁. It requires a garden hose for application.
- Roundup for Lawns 4 for southern grasses targets 90 different types of common weeds. It takes 4 hours to become rainproof.
Roundup Max Control 365
This deadly weed killer adds imazapic to the usual glyphosate formula to create one of the most effective herbicides out there.
It only takes about 30 minutes for the herbicide to become rainproof, and the initial effects will become visible after about 12 hours.
As with many other Roundup products, root death occurs in about 1 to 2 weeks.
But, this product continues to protect the ground for up to a year, making it the perfect product for use on driveways or sidewalks.
Roundup Poison Ivy Plus Tough Brush Killer
This product targets woody plants, such as poison ivy, poison oak, and unwanted shrubs.
The blend of glyphosate and triclopyr make it also effective as a stump killer.
It can take only 30 minutes to become rainproof, but you won’t see the initial signs working for about 24 hours.
Due to the various plants it targets, root death can take a few weeks or longer.
Roundup Precision Gel Weed & Grass Killer
One of the few downsides to glyphosate is that it can be an indiscriminate killer.
To help prevent damage to the plants you want, Roundup offers a precision gel stick.
The gel not only helps keep the herbicide on the plants you want to get rid of, but it also makes application easy.
The gel takes about 2 hours to become rainproof, although it begins working its way into the weed almost immediately.
You’ll usually note the first signs of yellowing or wilting in about 6 hours.
It will take between 1 and 2 weeks for this type of Roundup to work its way down to the roots, killing off the entire plant.
The formula is suitable for use in containers and garden spaces where plants are too close for sprays.
It’s also effective against annual and perennial weeds. You don’t have to worry about an existing weed returning once treated.
Roundup Ready-To-Use Weed & Grass Killer III
This premade glyphosate-based garden formula is compatible with various applicators, from precision nozzles to sprays.
It takes approximately 10 minutes for this product to become rainproof, and the initial results come quickly.
Expect to see the first signs of wilting and yellowing in as little as 3 hours.
It takes a little longer to kill the weed’s roots completely, usually about 1 to 2 weeks.
Which Roundup Should You Use?
Each Roundup formula works under specific circumstances, so you should avoid picking a formula based solely on how fast it works.
The formulas kill weeds without leaving toxins behind that could kill future plants.
Choose a Roundup product formulated for the task at hand to achieve the best results every time.
Driveways, Patios, and Sidewalks
- Roundup Extended Control Grass & Weed Killer Plus Weed Preventer II
- Roundup Max Control 365
Garden Use
- Roundup Precision Gel Weed & Grass Killer
- Roundup Ready-To-Use Weed & Grass Killer III
Lawn Care
- Roundup for Lawns
Woody Plants
- Roundup Poison Ivy Plus Tough Brush Killer