Tired of stubborn weeds ruining your lawn or garden? Post emergent weed killers offer an effective solution, targeting unwanted growth after it appears and restoring your outdoor spaces to perfection. In this shopping guide, we’ll explore top options and essential tips, helping you choose the right product to reclaim your yard and keep it looking its best, season after season.
Types of Post Emergent Weed Killer: At-a-Glance Comparison
| Type | Selectivity | Application Method | Speed of Results | Use Area Ideal For | Typical Active Ingredients | Kills Roots? | Safe for Lawns? |
|---|---|---|---|---|---|---|---|
| Selective, Systemic | Selective | Spray/Granular | 1–4 weeks | Lawns, turf, some gardens | 2,4-D, Dicamba, Mecoprop, etc. | Yes | Yes (if labeled) |
| Selective, Contact | Selective | Spray/Granular | Hours to days | Lawns, spot-treating | Iron HEDTA, Sulfentrazone | Partial | Yes |
| Non-selective, Systemic | Non-selective | Spray | 1–2 weeks | Driveways, patios, large areas | Glyphosate, Imazapyr | Yes | No |
| Non-selective, Contact | Non-selective | Spray | Minutes to hours | Walkways, beds, cracks | Fatty Acid Salts, Vinegar, Salt | Partial | No |
| Organic/Natural | Can vary | Spray | Hours to days | Vegetable beds, pet/play areas | Soap salts, vinegar, salt | No (usually) | Sometimes |
Everyday Usage: How Post Emergent Weed Killers Work
Post emergent weed killers are designed to eliminate weeds that are already visible and actively growing in your lawn, garden beds, driveways, or landscaped areas. Unlike pre-emergent products, which prevent weed seeds from sprouting, post emergent products attack the weed after it has surfaced.
Common Ways You Might Use Them
- Spot-treating: Targeting individual weeds or small clusters without affecting the entire area.
- Blanket applications: Treating areas with widespread infestations, especially in lawns or large beds.
- Clearing non-lawn areas: Removing all vegetation from driveways, patios, or fence lines.
- Restoring overgrown sections: Preparing garden beds or turf for reseeding by removing established weeds.
How They Work
Most post emergents work either by being absorbed through the leaves and then moving to the roots (systemic action), or by killing the plant tissue they make contact with (contact action). Systemic types are most effective for perennial and tough-to-kill weeds, while contact types provide fast visual results for annual or young weeds.
Key Benefits of Post Emergent Weed Killer
- Versatile control: Effective on a wide range of weeds, including broadleaf, grassy, and sedges.
- Flexible timing: Can be applied anytime weeds are actively growing—spring, summer, or fall.
- Garden and lawn friendly: Selective formulas target weeds without harming your desirable plants or grasses.
- Rapid transformation: Many products offer visible results in a matter of hours or days.
- Long-term impact: Systemic herbicides kill weeds right down to the root, reducing regrowth.
- Time and labor saver: Reduces the need for tedious hand-pulling or repeated manual weeding.
- Precision: Spot treatments help you target problem areas without widespread chemical exposure.
How to Choose the Right Post Emergent Weed Killer
Selecting the best post emergent weed killer depends on your specific situation, lawn type, and personal preferences. Here’s a step-by-step guide to help you decide:
1. Identify Your Weeds
- Are they broadleaf (dandelion, clover), grassy (crabgrass), or sedges (nutsedge)?
- Some herbicides are effective only against certain types.
2. Consider Selectivity
- Selective: Targets specific weeds, safe for most lawn types.
- Non-selective: Kills all plants it touches. Ideal for hard surfaces, total renovation, or non-planted areas.
3. Pick Application Method
- Spray (liquid): Good for spot-treating or covering uneven/large areas.
- Granular: Easy to apply with a spreader, ideal for beginner-friendly, uniform coverage.
4. Assess Application Area
- For lawns, use selective formulas.
- For non-lawn, gravel, driveways, or patios, non-selective is often best.
5. Check Weed Stage and Growth Conditions
- Post emergent herbicides work best when weeds are young and actively growing.
- Avoid applying during extreme heat (>85°F), drought, or after mowing.
6. Review Active Ingredients
- Determine product compatibility with your lawn and target weeds.
- Common actives:
- 2,4-D: Broadleaf weed control
- Dicamba: Broadleaf and tough weeds
- Quinclorac: Crabgrass
- Glyphosate: Non-selective, total kill
- Sulfentrazone: Sedges and some broadleaf
- Iron HEDTA: Organic option for lawns
- Salt/vinegar/fatty acids: Organic, non-selective
7. Prioritize Safety and Environmental Concerns
- For pet/play areas or near edibles, choose organic or low-risk options.
- Be mindful of water runoff and pollinator safety.
8. Evaluate Rainfast and Persistence
- Rainproof time indicates how soon after application rain won’t reduce effectiveness.
- Some formulations offer residual control for weeks or months.
Practical Tips and Best Practices for Choosing and Using Post Emergent Weed Killer
Before You Apply
- Read the label: Every product is different; always follow manufacturer recommendations.
- Wear protective gear: Gloves, long sleeves, pants, eye protection, and, for some chemicals, a mask or respirator.
- Check the weather: Pick a calm, rain-free day with temperatures below 85°F and above 55°F.
- Prepare the area:
- Don’t mow for 2–3 days before and after application.
- Remove debris and keep pets/kids away until the area is dry.
Application Tips
- Spot-treat when possible: Use a sprayer for individual weeds to limit chemical exposure.
- Blanket applications: For widespread issues, calibrate your spreader/sprayer and overlap slightly for even coverage.
- Avoid drift: Shield nearby ornamentals and edible plants; never apply in windy conditions.
- Watering:
- Most liquid sprays: Don’t water for 24 hours after application.
- For granular: Water in after application per label.
After Application
- Keep off the treated area until fully dry (usually 2–24 hours).
- Monitor results within 1–2 weeks. Reapply only if necessary and after waiting the recommended period.
- Clean your equipment: Separate tools used for herbicides from those used for fertilizers or pesticides.
Safety and Storage
- Store weed killers out of reach of children and pets.
- Use original containers, sealed tightly.
- Keep away from heat sources and direct sunlight.
Lawn Health
- Healthy, dense turf is your best defense against weeds.
- Reseed/replant only after the recommended interval following herbicide use.
Technical & Feature Comparison Table: Popular Post Emergent Weed Killers
| Product Name | Type | Active Ingredients | Selectivity | Application Area | Coverage per Unit | Rainfast Time | Visible Results | Lawns Safe For | Organic/Conventional |
|---|---|---|---|---|---|---|---|---|---|
| Southern Ag 2,4-D Amine | Liquid/Systemic | 2,4-D | Selective | Turf, parks, pastures | ~20,000 sq. ft. | 2 hours | 2–14 days | Most cool & warm season | Conventional |
| Ortho Weed B Gon Plus Crabgrass Ctrl | Liquid/Systemic | 2,4-D, Quinclorac, Dicamba | Selective | Established lawns | 5,000 sq. ft. | 1 hour | Hours–2 weeks | Bermuda, Zoysia, rye, blue/fescues | Conventional |
| Gordon’s SpeedZone Lawn Weed Killer | Liquid/Systemic | 2,4-D, Mecoprop, Dicamba | Selective | Lawns, blanket/spot | 14,000 sq. ft. | 3 hours | 24 hrs–2 weeks | Cool-season, Bermuda, Zoysia | Conventional |
| RM43 Total Vegetation Control | Liquid/Systemic | Glyphosate, Imazapyr | Non-selective | Paths, driveways, large areas | 4,300+ sq. ft. | 2 hours | 2–14 days | None (not for lawns) | Conventional |
| Spectracide Weed and Grass Killer | Liquid/Systemic | Diquat dibromide | Non-selective | Driveways, beds, patios | 5,400 sq. ft. | 15 min-1 hr | 3 hrs–2 days | None | Conventional |
| Captain Jack’s Lawnweed Brew | Liquid/Contact | Iron HEDTA | Selective | Most lawns, gardens | 2,400 sq. ft. | 1–2 hours | Within hours | Most cool/warm season (not bent) | Organic |
| Earth’s Ally Weed and Grass Killer | Liquid/Contact | Sodium Chloride | Non-selective | Beds, patios, walkways | 300 sq. ft. | 2 hours | 3 hours–10 days | None | Organic |
| Blindside WDG | Granular/Systemic | Sulfentrazone, Metsulfuron | Selective | Turfgrass (warm/cool) | 1,000+ sq. ft. | 4 hours | 1 week | Most major turfgrasses | Conventional |
Best Practices: How and When to Apply Post Emergent Weed Killer
- Identify the Target Weeds and Area
- Proper identification ensures effective selection (broadleaf, grassy, sedge, or mix).
-
For lawns, match your turf type to the product label.
-
Choose Application Method
- Use a hand-held or backpack sprayer for liquid products.
-
Use a drop or broadcast spreader for granules on large areas.
-
Timing Matters
- Apply when weeds are young and actively growing.
- Ideal times: late spring or early fall.
-
Avoid drought, heat waves, or after recent mowing.
-
Prepare Your Lawn and Equipment
- Don’t mow 2–3 days before or after application.
- Remove leaves, branches, and debris.
-
Mix the product precisely—don’t exceed label rates.
-
Apply Evenly and Carefully
- Spot-treat isolated weeds to protect turf.
- Use blanket approaches only for widespread weed infestations.
-
Shield desirable plants from overspray or drift.
-
Aftercare
- Keep pets and kids away from treated areas until dry.
- Water as instructed for granular formulations.
- Clean tools and store remaining product safely.
Related Video
Conclusion
Post emergent weed killers are powerful and versatile tools in any gardener’s or homeowner’s arsenal, offering an efficient solution to controlling weeds that have already sprouted. Whether you’re dealing with a few dandelions in your lawn, trying to eliminate crabgrass, or need to clear a driveway overtaken by vegetation, there’s a formula suited to your needs.
By understanding the differences among product types—selective versus non-selective, systemic versus contact, granular versus liquid—you can confidently pick the best solution for your landscape. Always prioritize correct identification, adherence to safety and application guidelines, and environmentally responsible use for optimal and lasting weed control.
FAQ
What is a post emergent weed killer?
A post emergent weed killer is a herbicide applied to weeds after they have emerged from the soil and are actively growing. It targets visible weeds rather than preventing new ones from sprouting.
Can I use post emergent weed killer on my lawn?
Yes, but only if you choose a selective formula labeled as safe for your specific grass type. Non-selective products will damage or kill lawn turf along with the weeds.
What’s the difference between selective and non-selective post emergent herbicides?
Selective herbicides target specific weeds (like broadleaf or grassy weeds) without affecting desirable grass, while non-selective herbicides kill all plants they contact. Use non-selective formulas with caution around desirable growth.
When is the best time to apply post emergent weed killer?
Apply when weeds are young and actively growing, typically in late spring or early fall with temperatures between 55°F and 85°F. Avoid application during drought, extreme heat, or right after mowing.
How long does it take for post emergent weed killer to work?
Visible results may appear from a few hours to two weeks, depending on the product and weed species. Systemic varieties may take longer (up to four weeks) as they travel to roots.
Can I mix post emergent weed killer with fertilizer (weed and feed)?
Some products combine herbicides and fertilizer as “weed and feed”. However, simultaneous fertilizing and weed killing may not always be ideal for lawn health. Use with caution and follow label instructions for your grass and climate.
Will rain affect the effectiveness of post emergent weed killer?
Many products are rainfast within one to four hours, but rainfall before the product dries or is absorbed can reduce effectiveness. Check the product label for the minimum rainfast time and avoid application before expected rain.
Is it safe to use post emergent weed killer around children or pets?
Allow treated areas to dry completely before permitting children or pets to re-enter. For added safety, choose organic-based or low-toxicity options in play and pet zones.
How much area does one bottle or bag cover?
Coverage varies by product and application rate. Example: 32 oz of liquid concentrate may cover 14,000–64,000 sq. ft. for lawns; ready-to-use sprays often cover only a few hundred sq. ft. Always read and calculate based on label guidance.
What should I do if I accidentally spray desirable plants?
Rinse affected plants immediately with lots of water to dilute and remove the herbicide. Some damage may still occur, especially with non-selective products. For lawns, avoid overlapping or overapplying to prevent turf injury.