Will Rain Wash Away My Weed Control Treatment?
One of the most common lawn care questions we get is: “It just rained—will that ruin the weed control treatment on my lawn?”
In most cases, rain doesn’t hurt weed control, and sometimes it even helps! At bioLawn, we use professional-grade products that are rain-tolerant and designed to work in Midwest weather. Here’s how rain really impacts your weed treatment—and what to watch for.
How Weed Control Works: Rain and Lawn Treatments Explained
We use dual-action weed control that works in two ways:
- Foliar absorption: The solution is absorbed through the leaves of the weeds.
- Root uptake: Rain carries some product into the soil where it’s absorbed by the roots.
Our formula includes an additive that helps the product adhere to the weed’s surface and begin absorbing quickly. That means even if it rains shortly after an application, the treatment can still be effective.
Real Results: Weed Control After Heavy Rain
We put our products to the test. Both in the field and through funding University reserach. Recently, we treated dandelions and crabgrass less than 30 minutes before a downpour. That storm dropped rain at a rate of 1 inch per hour.
Five days later, the weeds were already turning brown and purple, showing the treatment had taken effect—even after heavy rain quickly after a treatment
Ten days later, the weeds were dying furhter, showing the treatment continued to work—even after heavy rain quickly after a treatment
Not All Rain Is The Same. How Rain Affects Weed Control Effectiveness
1. How Much Did It Rain?
- A little bit of rain: Even if immediately after application, often helps by moving the weed control into the soil where the roots can absorb it.
- A lot of rain: Can be fine if the rain falls slowly over several hours.
2. How Soon After Treatment Did It Rain?
- The product starts working within 15–30 minutes. So independent of how much, if the rain came after that, the treatment likely absorbed enough to be effective.
3. What Kind of Weeds Were Treated?
- Easy to control weeds (like dandelions or broadleaf plantain): Often die with only a little bit of weed control and thus rainfall amount or timing typically doesn’t change control.
- Hard to control weeds (like crabgrass or violets): Need to absorb more weed control, and thus rain can effect the control of these weeds more.
4. Is the Weed Actively Growing?
- Actively growing weeds absorb the product better and thus rain has less of an effect.
- Weeds under drought stress may take longer to respond, leading to a greater reduction in control from rainfall.
Be Patient—Weed Control Takes Time
Even in perfect conditions, it can take 7–10 days for treated weeds to decline after a treatment.
If you’ve had rain after a treatment, give it a little time. The product may already be working below the surface—even if you don’t see immediate results.
And if weeds are still hanging around after a week? That’s where our Healthy Grass Guarantee comes in. If you’re on a full lawn care program, we’ll retreat at no charge. Just give us a call.
Why We Spray Even When Rain Is in the Forecast
You might wonder: “If rain is coming, why apply weed control at all?”
Weather in the Midwest is unpredictable. Waiting for a “perfect forecast” would delay service and lead to more weeds in the lawn. Instead, we rely on fast-absorbing, rain-resistant products to get results. We back up our applications with a Healthy Grass Guarantee, which means if it doesn’t work, we will be back out to fix it.
This helps ensure your lawn stays on track—rain or shine.
Final Thoughts: Rain Doesn’t Always Hurt Weed Control
The idea that rain ruins weed control is a myth.
In many cases, rain helps with absorption and actually improves root uptake. At bioLawn, we’ve selected and tested our products to perform in real-world weather—so your lawn can thrive.