RM43 Vs. Roundup: A Head-to-Head Showdown For Weed Control

I’ve spent countless weekends battling weeds in my yard, from stubborn dandelions creeping through my driveway cracks to rogue grasses invading my garden beds. If you’re like me, you want a weed killer that works fast, lasts long, and doesn’t break the bank.

That’s why I’m comparing two heavyweights in the weed control world: RM43 and Roundup. My goal is to break down their features, pros, cons, and real-world performance to help you decide which one suits your needs.

Let’s get into the comparison and find the best solution for your weed woes.

A Brief Comparison Table

My Journey With Weeds

I’ve always taken pride in my yard, but weeds have a way of testing my patience. Last summer, I noticed crabgrass and thistles taking over my gravel pathway, and no amount of pulling seemed to keep them at bay.

I needed a solution that wouldn’t just knock them out temporarily but keep them gone. That’s when I started researching RM43 and Roundup, two names that kept popping up in gardening forums and hardware store aisles.

Both are glyphosate-based, but their differences in ingredients, longevity, and application make them suited for different tasks. Let me share what I’ve learned through trial, error, and a lot of spraying.

Understanding RM43: The Heavy-Duty Weed Annihilator

RM43 is like the nuclear option for weeds.

It’s a non-selective herbicide, meaning it wipes out everything it touches—grasses, broadleaf weeds, vines, even small trees if you’re not careful.

Its formula combines glyphosate (43%) with imazapyr (0.78%), a second herbicide that gives it staying power.

The glyphosate kills existing plants by disrupting their growth processes, while imazapyr lingers in the soil, preventing new growth for up to a year.

I first used RM43 on a patch of my driveway where weeds kept sprouting through the cracks. The results? Impressive, but it’s not a one-size-fits-all solution.

Pros of RM43

• Long-Lasting Control: The standout feature of RM43 is its ability to prevent weed regrowth for up to 12 months. I sprayed it on my gravel path last spring, and by fall, I still hadn’t seen a single weed poke through.
• Broad-Spectrum Power: It tackles a wide range of plants, from tough crabgrass to woody vines. I found it especially effective on stubborn perennials that kept coming back.
• High Coverage: One gallon of RM43 concentrate can treat up to 43,243 square feet when mixed properly. For large areas like fence lines or parking lots, this makes it cost-effective.
• Rainproof in Two Hours: I live in an area with unpredictable showers, and RM43’s quick rainproof time saved me from worrying about wash-off.
• Versatile Application: Whether you’re clearing bare ground or spot-treating brush, RM43 handles it all. I used it around my barn, and it kept the area weed-free for months.

Cons of RM43

• Overkill for Small Jobs: RM43’s long-lasting soil activity makes it a poor choice for areas where you plan to replant soon. I learned this the hard way when I tried to plant grass seed in a treated spot—nothing grew for nearly a year.
• Higher Cost: At $80–$100 per gallon, RM43 is pricier than many Roundup products. If you’re just spot-treating a few weeds, it might feel like overpaying.
• Environmental Concerns: The addition of imazapyr makes RM43 more persistent in the soil, which can harm nearby plants if you’re not precise. I accidentally killed a shrub near my application area because of drift.
• Safety Risks: Both glyphosate and imazapyr have raised health concerns, with glyphosate classified as a probable carcinogen by the IARC in 2015. I always wear gloves, a mask, and long sleeves when spraying.
• Complex Mixing: RM43 requires careful dilution (6–7.4 oz per gallon), and I found myself double-checking measurements to avoid wasting product or under-dosing.

Exploring Roundup: The Household Name in Weed Control

Roundup is the go-to for many homeowners, and I get why.

It’s been around since the 1970s, and its glyphosate-based formula (41–50.2%, depending on the product) is a proven weed killer.

Unlike RM43, Roundup is primarily a post-emergent herbicide, meaning it targets plants that are already growing.

It’s available in various forms—concentrates, ready-to-use sprays, and even versions with extended control up to four months.

I’ve used Roundup for spot-treating weeds in my lawn and garden beds, and its ease of use is hard to beat.

Pros of Roundup

• Fast-Acting: Roundup starts yellowing weeds within 2–48 hours, though full kill takes 7–14 days. I sprayed some dandelions in my lawn, and they were wilting by the next day.
• Affordable Options: Prices vary, but a gallon of Roundup concentrate can cost as little as $20–$60. For small jobs, it’s easier on the wallet than RM43.
• Flexible Use: Roundup is ideal for areas where you want to replant soon. I cleared a weedy garden bed with Roundup and planted new flowers a week later with no issues.
• Wide Availability: You can find Roundup at any hardware store or online. I grabbed a ready-to-use bottle at Home Depot when I needed a quick fix.
• Less Soil Persistence: Since it’s primarily glyphosate, Roundup becomes inert in the soil quickly, reducing the risk of long-term damage to nearby plants.

Cons of Roundup

• Shorter-Lasting Control: Standard Roundup doesn’t prevent new weeds from sprouting. I found new weeds popping up a month after treating my driveway.
• Limited Against Tough Weeds: While effective on most annuals, Roundup struggles with woody plants or deep-rooted perennials. I had to reapply it multiple times to kill a stubborn vine.
• Health Concerns: Like RM43, Roundup’s glyphosate is controversial. I make sure to follow safety guidelines to minimize exposure.
• Multiple Applications Needed: For persistent weeds, you might need to spray several times. I got frustrated re-treating the same patch of crabgrass.
• Dilution Confusion: Concentrate versions require mixing (1.5–2.5 oz per gallon), and I’ve heard friends complain about getting the ratio wrong.

Key Features Comparison of RM43 And Roundup

Let’s talk specifics. RM43’s dual-action formula (glyphosate + imazapyr) makes it a beast for total vegetation control. It’s designed for areas where you want nothing growing—like driveways, patios, or fence lines.

I used it on a gravel lot behind my house, and it kept the area barren for a full year.

The trade-off?

You can’t plant anything there afterward without waiting. Roundup, on the other hand, is more forgiving.

Its glyphosate-only formula (or with additives in extended-control versions) is perfect for spot-treating or clearing areas before replanting.

I used Roundup’s ready-to-use spray on weeds near my roses, and it didn’t harm the flowers when applied carefully.

RM43’s coverage is a big selling point. A single gallon can treat massive areas, making it ideal for large properties. I calculated that my 1-gallon jug covered about 17,000 square feet at the recommended mix rate.

Roundup’s coverage varies by product, but concentrates typically cover less per gallon. For example, Roundup Super Concentrate covers about 300 square feet per gallon when mixed, which is fine for small yards but less practical for big jobs.

Rainproof time is another factor. Roundup’s 30-minute rainproof window is faster than RM43’s two hours, which mattered when I was racing against a storm. Both take 7–14 days to fully kill weeds, but I noticed Roundup’s visible effects (yellowing) slightly sooner.

However, RM43’s pre-emergent action means fewer follow-up treatments, which saved me time in the long run.

My Experience With RM43 And Roundup

To really understand these products, I tested them head-to-head. My backyard has a mix of challenges: a gravel driveway with persistent weeds, a lawn with dandelions, and a fence line overrun with thistles.

I used RM43 on the driveway and fence line, mixing 6 oz per gallon in a backpack sprayer. The weeds started browning after a few days, and by two weeks, they were completely dead.

Six months later, the treated areas were still weed-free, which was a huge win for my low-maintenance goals.

For the lawn, I chose Roundup’s ready-to-use spray with the Comfort Wand. I targeted dandelions and clover, being careful to avoid my grass. The weeds yellowed within 24 hours, and by day 10, they were gone.

But a month later, new weeds sprouted in the same spots, so I had to reapply. Roundup was easier to use for precise applications, but RM43’s longevity made it the better choice for areas I wanted to keep bare.

Safety And Environmental Considerations

Both products use glyphosate, which has sparked debate due to its classification as a probable carcinogen by the IARC. While the EPA in 2020 stated glyphosate is unlikely to cause cancer when used as directed, I take no chances.

I wear protective gear—gloves, goggles, and a mask—and avoid spraying on windy days. RM43’s imazapyr adds another layer of concern, as it persists in the soil and can affect nearby plants. I learned this when runoff from my driveway treatment damaged a nearby bush.

Roundup’s soil inactivity is a plus here, but you still need to be cautious to avoid overspray.

Environmentally, RM43’s long soil persistence can be a double-edged sword. It’s great for keeping weeds at bay, but it’s risky near water sources or desirable plants.

Roundup, while less persistent, still requires careful application to avoid harming non-target plants. I’ve started exploring alternatives like vinegar-based sprays for smaller jobs, but they don’t match the power of these chemical herbicides.

Cost Vs. Value: Which Offers More Bang For Your Buck?

RM43’s higher price tag ($80–$100 per gallon) reflects its potency and longevity.

For large-scale projects, like clearing a half-acre lot, it’s worth the investment.

I spent about $90 on a 2.5-gallon jug of RM43, and it lasted me two seasons of heavy use.

Roundup is cheaper upfront, with concentrates starting at $20, but you might need more frequent applications.

For my small lawn treatments, a $30 bottle of Roundup concentrate was enough, but I had to budget for follow-up sprays.

If you’re tackling a big, weed-infested area and want a one-and-done solution, RM43’s cost is justified. For smaller, recurring jobs, Roundup’s lower price and flexibility make it more practical. I’ve learned to keep both in my shed, choosing based on the task at hand.

Application Tips From My Mistakes

Using these products effectively takes some know-how. With RM43, I initially mixed too little (4 oz per gallon), and the weeds took longer to die. Stick to the 6–7.4 oz per gallon ratio for best results.

I also learned to spray early in the morning when it’s less windy to avoid drift. For Roundup, the ready-to-use spray is a lifesaver for quick jobs, but the concentrate requires precise mixing. I once diluted it too much and got weak results, so now I use a measuring cup religiously.

Always read the label—both products have specific instructions for different weeds and areas. I made the mistake of using RM43 too close to my garden, and the imazapyr killed some of my vegetables.

With Roundup, I’ve had success using a paintbrush to apply it directly to weed leaves in tight spaces, minimizing damage to nearby plants.

Choosing The Right Product For You

Your choice depends on your goals. If you’re like me and have a large area—like a driveway or fence line—that you want weed-free for a year, RM43 is your best bet. Its pre-emergent action saves you from constant re-spraying.

But if you’re spot-treating weeds in a lawn or garden and plan to replant soon, Roundup is the safer, more affordable option. I’ve used both successfully, but I lean toward RM43 for permanent solutions and Roundup for quick, targeted fixes.

Frequently Asked Questions (FAQ)

Conclusion: Your Weed-Free Future Awaits

After testing RM43 and Roundup in my own yard, I’ve seen firsthand how they tackle weeds differently. RM43 is your go-to for long-lasting, total vegetation control—perfect for driveways or bare ground where you want nothing growing.

Roundup, with its quick action and flexibility, is ideal for spot treatments and areas you’ll replant. Both have their place, but your choice depends on your specific needs.

Whether you’re battling a jungle of weeds or just a few pesky dandelions, pick the right tool, follow the instructions, and you’ll reclaim your outdoor space in no time.