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Morning glory vines are relentless. Their deep, sprawling root systems and rapid growth can strangle flower beds, climb fences, and overtake vegetable gardens in a single season. A targeted herbicide is the only reliable way to break their cycle without resorting to endless hand-pulling.
I’m Mohammad Maruf — the founder and writer behind Gardening Beyond. I study herbicide formulation data, compare active ingredient concentrations, and analyze aggregated owner feedback to identify which products deliver the most effective control against stubborn perennial vines like morning glory.
Whether you need a spot-treatment spray or a large-area concentrate, this guide breaks down the specific formulations that tackle morning glory at the root. My goal is to help you find the right morning glory herbicide for your specific weed pressure and yard size.
How To Choose The Best Morning Glory Herbicide
Morning glory’s taproot can extend several feet deep, storing energy that allows it to resprout after surface treatments. The right herbicide must be systemic — absorbed by the leaves and transported to the roots. Here are the key factors to consider.
Active Ingredient: Glyphosate vs. Triclopyr
Glyphosate is a non-selective systemic herbicide that works well on annual and perennial weeds. For mature morning glory, a concentration of 41% glyphosate (like in Compare-N-Save) provides reliable root kill. Triclopyr, found in brush killers like Image, is often more effective on woody vines and can persist longer in plant tissue. Some products combine both for a broader spectrum.
Concentrate vs. Ready-to-Use
Concentrates require mixing with water in a tank sprayer but offer far better value per square foot of coverage. A 32-ounce concentrate can treat over 1,000 square feet, while a ready-to-use spray may cover only 100-200 square feet per bottle. For large infestations of morning glory, a concentrate is the only economical choice.
Rainfast Window
Rainfastness — how soon after application rain won’t wash off the chemical — ranges from 15 minutes to 2 hours. Products like Ortho GroundClear (15 minutes rainfast) are ideal for unpredictable weather. Slower-absorbing formulas require a longer dry period for maximum efficacy.
Pre-Emergent vs. Post-Emergent
Post-emergent herbicides kill existing morning glory vines. Some products, like Roundup Dual Action, also include a pre-emergent component that prevents new seeds from germinating for up to 4 months. This two-stage approach is valuable in beds where morning glory seeds remain in the soil.
Quick Comparison
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| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| Compare-N-Save 75324 | Concentrate | Large-scale vine control | 41% Glyphosate, 1 gallon | Amazon |
| Roundup Dual Action | Preventer | Long-term weed prevention | 4-month pre-emergent barrier | Amazon |
| Ortho GroundClear | Super Concentrate | Fast-kill on tough weeds | 2,4-D + Dicamba, 15 min rainfast | Amazon |
| Image Brush & Vine Killer | Brush Concentrate | Poison ivy & brush vines | Triclopyr-based, 32 oz | Amazon |
| Spectracide Weed & Grass Killer | Fast-acting | Quick visible results | Diquat Dibromide, 3-hour results | Amazon |
In‑Depth Reviews
1. Compare-N-Save 75324 Herbicide, 1-gallon
The Compare-N-Save 75324 is the heavy hitter for large properties. With a full gallon of 41% glyphosate concentrate, it makes up to 85 gallons of ready-to-use spray and covers over 25,000 square feet. This is easily the most cost-effective option per square foot for tackling widespread morning glory infestations across fence lines, pastures, or large garden beds.
Customers consistently report that it kills weeds completely, including deep-rooted vines, but they also note it works slower than some competitors — expect visible results in 2 to 4 days, with full root death taking up to a month. The slower action is typical of high-concentration glyphosate, which needs time to translocate to the entire root system.
One caution: the gallon jug can arrive with a loose cap, and the packaging is minimal. Always check the seal upon delivery and store it upright. Despite this, the overwhelming consensus is that it performs identically to name-brand Roundup at a fraction of the cost per gallon of mixed spray.
What works
- Exceptional value — makes 85 gallons of spray
- 41% glyphosate concentration matches premium brands
- Proven systemic kill on deep-rooted perennials like morning glory
What doesn’t
- Slow visible results — takes weeks for full effect
- Jug packaging can leak during shipping
2. Roundup Dual Action Weed & Grass Killer Plus 4 Month Preventer Concentrate
The Roundup Dual Action concentrate is unique because it combines a fast-acting post-emergent killer with a pre-emergent barrier that prevents new morning glory seeds from sprouting for up to 4 months. For gardeners fighting repeated regrowth from seed banks in the soil, this two-stage chemistry is a significant advantage over standard glyphosate-only products.
Users report visible wilting within 6 hours on broadleaf weeds like morning glory, and the rainfast window of 30 minutes is solid for most weather conditions. The formula is designed for use on hardscapes, gravel areas, and around well-established trees and shrubs — not for use directly in vegetable beds or near desirable plants you want to keep.
A few long-time Roundup users note that the concentrate feels less potent than older formulations, and the price per ounce is higher than generic alternatives. However, the convenience of getting both kill and prevention in one bottle eliminates the need for a separate pre-emergent application, saving time on large properties.
What works
- Post-emergent kill plus 4-month pre-emergent prevention
- Visible results as fast as 6 hours on sensitive weeds
- Rainproof in 30 minutes
What doesn’t
- Higher cost per ounce than generic glyphosate concentrates
- Not suitable for use near desired ornamental plants
3. Ortho GroundClear Weed and Grass Killer Super Concentrate
The Ortho GroundClear Super Concentrate is a broad-spectrum formula built for speed. It contains 2,4-D and Dicamba, two selective broadleaf herbicides that work synergistically to kill tough weeds like morning glory, clover, and dandelion to the root. Users consistently report seeing results within 2 to 48 hours, making it one of the fastest-acting concentrates available.
A key advantage is its 15-minute rainfast window — the shortest on this list. If you’re spraying in a climate with frequent afternoon showers, this product gives you the best chance of keeping the chemical on the leaves long enough to work. Each 32-ounce bottle treats up to 1,120 square feet at standard mix rates, or up to 2,240 square feet at lower rates.
One important caveat: the 2,4-D and Dicamba formulation is volatile above 80°F, meaning it can vaporize and drift onto nearby desirable plants, causing damage. Avoid applying on hot, windy days, and never use it near sensitive ornamentals or vegetable gardens. For purely hardscape or fence-line morning glory, it’s a powerhouse.
What works
- Extremely fast visual results in 2-48 hours
- 15-minute rainfast window is industry-leading
- Cost-effective concentrate makes multiple gallons
What doesn’t
- Volatile above 80°F — risk of drift damage
- Not for use near desired plants or edible gardens
4. Image Brush & Vine Killer Concentrate
The Image Brush & Vine Killer is specifically formulated for woody vines and tough brush, including poison ivy, wild blackberry, kudzu, and morning glory. Its active ingredient, triclopyr, is a systemic herbicide that moves through the vascular system more aggressively than glyphosate on woody species, providing “roots and all” kill without regrowth from underground crowns.
User reviews highlight its effectiveness on Himalayan blackberry — a notoriously resilient vine — at higher mix rates (5 ounces per gallon). For morning glory, a standard 4 ounces per gallon is typically sufficient, though yellowing may take 7-10 days. A surfactant is recommended to improve leaf adhesion, especially on the waxy leaves of mature morning glory vines.
One notable drawback is that triclopyr can cause throat irritation if overspray is inhaled, so a respirator or at minimum a dust mask is advisable during application. The 32-ounce concentrate covers up to 4,000 square feet, making it a solid mid-range option for targeted vine control on smaller properties.
What works
- Effective on woody vines where glyphosate may fail
- Systemic root kill — no regrowth from underground crowns
- Good value for targeted spot treatment of vines
What doesn’t
- Works slowly on established vines — up to 4 weeks
- Requires surfactant for best results on waxy leaves
5. Spectracide Weed and Grass Killer Concentrate
The Spectracide Weed and Grass Killer Concentrate uses diquat dibromide, a contact herbicide that desiccates plant tissue rapidly — visible results in as little as 3 hours. This makes it an excellent choice for quick cleanups on driveways, walkways, and fence lines where you want immediate aesthetic improvement.
However, diquat is a contact killer, not a systemic killer. It does not translocate to the root system. For morning glory, this means the top growth will die quickly, but the deep taproot often survives and resprouts. The product is best used as a spot-treatment for young, tender morning glory seedlings or as a maintenance tool after initial systemic treatment has killed the root.
The Accumeasure measuring system on the cap is a thoughtful touch for precise mixing, though some users find it finicky and replace it with a standard cap. At 32 ounces covering 1,350 square feet, it’s a budget-friendly option for small areas, but it should not be relied upon as the sole weapon against established morning glory infestations.
What works
- Extremely fast visible results in 3 hours
- Rainfast in only 15 minutes
- Budget-friendly price for small areas
What doesn’t
- Contact killer only — does not kill roots of deep perennials
- Morning glory regrowth common after initial top kill
Herbicide Specs Guide
Active Ingredient Types
Glyphosate is the most common non-selective systemic herbicide, effective on a broad spectrum of annual and perennial weeds including morning glory. Triclopyr targets woody vines and brush more aggressively. Diquat dibromide is a contact herbicide that kills top growth quickly but doesn’t reach roots. Products like Ortho GroundClear use a 2,4-D and Dicamba blend for fast broadleaf-specific kill.
Coverage Area
Coverage is measured in square feet per bottle at standard mix rates. A 32-ounce glyphosate concentrate typically covers 1,000-2,000 square feet. A gallon of 41% glyphosate covers over 25,000 square feet. Always calculate the size of your infestation — morning glory spreads rapidly, and underestimating coverage means additional trips to the store.
Rainfast Time
Rainfastness is the minimum time between application and rainfall needed for the herbicide to be effective. Products range from 15 minutes (Ortho GroundClear, Spectracide) to 2 hours (Compare-N-Save). Rain before the rainfast window washes the active ingredient off the leaves, requiring reapplication. Check your local forecast before spraying.
Surfactant Requirement
Some herbicides, particularly those with triclopyr, benefit from a surfactant (non-ionic surfactant or a few drops of dish soap). Surfactants reduce the surface tension of water droplets, allowing the herbicide to spread evenly and adhere to waxy leaves like those of mature morning glory. Without a surfactant, bead-up and runoff can reduce efficacy significantly.
FAQ
Will glyphosate kill morning glory roots for good?
What is the best time of year to spray morning glory?
Can I use these herbicides in my vegetable garden?
Final Thoughts: The Verdict
For most gardeners battling morning glory, the morning glory herbicide winner is the Compare-N-Save 75324 because it delivers 41% glyphosate at the lowest cost per gallon of mixed spray, covering over 25,000 square feet. If you want a dual-action product that kills existing vines and prevents regrowth from seeds, grab the Roundup Dual Action. And for rapid visible results on tough brush, nothing beats the Ortho GroundClear Super Concentrate.