Ortho Weed & Grass Killer Concentrate 32oz

The minute-by-minute action matters more than the organic label. Ortho’s 6.35% Ammonium Nonanoate formula delivers visible results in approximately 15 minutes — fast enough to show clients you’re solving their weed problem before you leave the jobsite. At 300 sq ft coverage per gallon of mix, this concentrate handles hardscape and non-lawn areas where you need organic certification without the wait time of traditional organic options.

Skip it for anything over 3 inches tall or if you’re promising one-and-done results. This contact herbicide only kills on contact (does not kill roots of tough weeds), meaning established perennials laugh it off and come back. The OMRI Listed for organic gardening certification opens doors for environmentally-conscious clients, but don’t oversell the capability — this works on young weeds, not mature stands.

Fast Action Meets Organic Standards

The 6.35% Ammonium Nonanoate active ingredient represents the sweet spot between organic certification and actual performance. Unlike household vinegar solutions that take hours to show any effect, this fatty acid derivative disrupts cell membranes on contact. You’ll see wilting and browning start within approximately 15 minutes — critical for demonstrating value to watching customers.

The 2 hours after application (once dry) rainproof window works with Montana’s afternoon thunderstorm patterns. Apply in the morning when weeds are turgid, get your visible results, and you’re protected before the typical 2 PM weather rolls in. That two-hour window beats most conventional herbicides that need 4-6 hours.

Specification	Value
Active Ingredient	Ammonium Nonanoate (6.35%)
Visible Results	Approximately 15 minutes
Rainproof Time	2 hours after application (once dry)
Physical Form	Liquid Concentrate
Package Size	32 fl. oz.

Coverage Math That Actually Works

Forget the marketing fluff — here’s what matters for job costing. Mix 16 to 19.2 fl. oz. per gallon of water, which gives you roughly a 1:8 dilution ratio. Each gallon of mixed solution covers 300 sq. ft., so the 32 fl. oz. bottle yields two gallons of spray mix for 600 sq. ft. total coverage.

That coverage rate assumes thorough foliar wetting — and with contact herbicides, coverage equals control. Light misting won’t cut it. You need complete leaf surface coverage, which means your actual square footage might run lower if you’re dealing with dense weed growth. Factor that into your estimates.

Mix the concentrate with water according to label (approx 1:8 ratio) translates to simple field math: one part concentrate to eight parts water. No complex calculations, no specialized measuring equipment. A standard pump sprayer with gallon markings handles the job.

Contact-Only Reality Check

Here’s what the label won’t emphasize: Only kills on contact (does not kill roots of tough weeds). This isn’t a systemic herbicide. It burns down green tissue it touches, period. Best applied when weeds are young and small (< 3 inches) because once tap roots develop or rhizomes establish, you’re just mowing with chemicals.

Requires multiple applications for larger weeds — and that’s being generous. Established bindweed, Canada thistle, or quackgrass will green up again within weeks. Set client expectations accordingly. This product excels at maintaining clean hardscapes when applied regularly, not reclaiming neglected areas.

The Non-selective (kills weeds and grasses) nature means drift control matters. Apply on a dry day with no wind to avoid drift, especially near ornamental beds or lawn edges. Even minor overspray browns out desirable plants within hours.

Frequently Asked Questions

How fast do results actually appear? Results visible in approximately 15 minutes. You’ll see wilting and color change start almost immediately on actively growing weeds. Complete browning takes 24-48 hours depending on weed type and growing conditions.

What’s the actual coverage area per bottle? Up to 600 sq. ft. per 32 fl. oz. bottle. That’s based on proper dilution at 16 to 19.2 fl. oz. per gallon of water, with each gallon covering 300 sq. ft.

Will this kill tough perennial weeds? No. Only kills on contact (does not kill roots of tough weeds). It’ll burn down the green growth, but anything with established roots or rhizomes regrows. Requires multiple applications for larger weeds.

Is this safe around pets and kids? Safe for pets and children once the applied spray has dried completely. The 2 hours after application (once dry) rainproof time also serves as your re-entry guideline.

What surfaces work with this product? Surface safe: compatible with concrete, asphalt, pavers, and mulch. It’s designed for Hardscapes: patios, driveways, walkways and Landscape areas: flower beds, mulch areas, under trees.