Ortho Weed B Gon Chickweed Clover & Oxalis Killer Dosage Guide

The Chemistry of Broadleaf Eradication

Ortho Weed B Gon Chickweed, Clover & Oxalis Killer Concentrate relies on a three-way synergistic herbicide blend to target stubborn broadleaf weeds without harming established turfgrass. The formulation typically combines 2,4-D, MCPP-p (mecoprop), and Dicamba. Understanding how these active ingredients interact is critical for maximizing efficacy and preventing turf damage.

While 2,4-D acts as a systemic auxin mimic that disrupts cell division in broadleaf plants, it is often less effective on mature clover or deep-rooted oxalis. The inclusion of MCPP-p specifically targets clover and chickweed species, while Dicamba provides the soil-residual and systemic action required to kill oxalis (woodsorrel) and its deep taproots. According to the Environmental Protection Agency (EPA), Dicamba is highly mobile in soil, which is precisely why adhering to exact dosage rates is mandatory to prevent leaching into desirable flower beds or root zones of shallow-rooted ornamentals.

Exact Dosage and Mixing Rates by Grass Type

The most common failure mode when using this concentrate is overdosing, which leads to severe phytotoxicity (yellowing and stunting of the turfgrass). The dosage is not one-size-fits-all; it varies based on your specific turf species and its inherent tolerance to synthetic auxins.

Step-by-Step Mixing Protocol

To ensure a homogenous suspension and prevent the active ingredients from settling at the bottom of the tank, follow this exact mixing order:

1. Pre-fill: Fill your pump sprayer tank with exactly half of the required water volume (e.g., 0.5 gallons for a 1-gallon mix).
2. Measure: Using a dedicated plastic measuring cup (never use kitchenware), measure the exact fluid ounces of concentrate required for your grass type.
3. Agitate: Pour the concentrate into the tank and gently swirl the sprayer to initiate mixing.
4. Top Off: Add the remaining water to reach the 1-gallon mark. The turbulence from the incoming water will complete the mixing process.
5. Pressurize: Seal the tank and pump to 40-50 PSI. Do not over-pressurize, as this creates a fine mist that increases the risk of herbicide drift onto non-target plants.

Coverage Area and 2026 Cost Breakdown

When evaluating the return on investment for DIY lawn care versus hiring a professional service, the concentrate format offers massive economies of scale compared to ready-to-spray hose-end bottles. As of early 2026, retail pricing for this concentrate at major home improvement centers is as follows:

• 16 oz Bottle: ~$17.98 | Yields 8 gallons of mixed solution | Covers 4,000 sq ft
• 32 oz Bottle: ~$28.48 | Yields 16 gallons of mixed solution | Covers 8,000 sq ft

Cost Per 1,000 Square Feet:
Using the 16 oz bottle, your chemical cost is approximately $4.50 per 1,000 sq ft. Using the 32 oz bottle drops this to $3.56 per 1,000 sq ft. By comparison, a professional lawn care company (like TruGreen or a local licensed operator) typically charges between $15.00 and $25.00 per 1,000 sq ft for a targeted broadleaf spot-treatment visit. Over a standard 5,000 sq ft suburban lawn, DIY application saves roughly $60 to $100 per treatment cycle.

Environmental Constraints and Application Timing

The efficacy of 2,4-D, MCPP-p, and Dicamba is heavily dependent on environmental conditions. Applying the product outside of these parameters will result in poor weed control or turf damage.

Temperature Thresholds

Apply only when daytime air temperatures are between 60°F and 85°F. When temperatures exceed 85°F, the active ingredients (particularly 2,4-D and Dicamba) are prone to volatilization. This means the liquid turns into a gas and drifts through the air, potentially damaging neighboring gardens, tomato plants, and ornamental shrubs. Furthermore, turfgrass is already under heat stress above 85°F, making it highly susceptible to chemical burn.

Rainfastness and Soil Moisture

According to turfgrass management guidelines from NC State TurfFiles, systemic herbicides require adequate soil moisture to be translocated effectively through the weed's vascular system. Water your lawn deeply 24 hours before application. The product becomes rainfast in 6 hours. If a heavy downpour occurs within 4 hours of application, the treatment will likely wash off the leaf cuticle, requiring a reapplication at half the original dosage.

Troubleshooting Common Application Failures

Even with precise measurements, variables in the field can alter outcomes. Here is how to diagnose and correct common issues:

• Symptom: Weeds are wilting, but the surrounding turfgrass is turning pale yellow.
  Cause: Overdose or application during high heat.
  Fix: Stop applications immediately. Apply a liquid kelp extract or a light dose of granular nitrogen (0.5 lbs per 1,000 sq ft) to help the turfgrass metabolize the herbicide stress. Do not reapply for at least 45 days.
• Symptom: Clover and chickweed are unaffected after 14 days.
  Cause: Application made to mature, drought-stressed weeds with thick waxy cuticles.
  Fix: Mow the lawn to remove the top layer of the weed canopy, wait 3 days for fresh, tender growth to emerge, and reapply at the standard rate. Adding a non-ionic surfactant (1/2 teaspoon per gallon) can also help the chemical penetrate the waxy leaf surface.
• Symptom: Oxalis returns in the exact same spot 3 weeks later.
  Cause: Oxalis grows from deep, brittle taproots and bulbils. A single application often only kills the top growth.
  Fix: A second application is mandatory for oxalis control. Wait 21 to 30 days after the first application and re-treat the specific patches.

Frequently Asked Questions

Can I mix this concentrate with liquid fertilizer?

While tank-mixing with liquid fertilizers (like 20-0-0 urea solutions) is common in commercial turf management to save time, it is not recommended for homeowners using this specific Ortho concentrate. The high salt index of liquid nitrogen can alter the pH of the spray solution, reducing the stability of the Dicamba and causing the mixture to precipitate (clump) inside your sprayer nozzle.

Is it safe for pets and children?

The product is safe for pets and children once the liquid spray has completely dried on the grass blades, which typically takes 2 to 4 hours depending on humidity and sunlight. Keep all people and animals off the treated area during application and until the turf is visibly dry.

How should I store the leftover concentrate?

Store the bottle in a cool, dry place where temperatures do not drop below freezing. Freezing can cause the emulsifiers in the concentrate to break down, resulting in a separated mixture that will not re-suspend properly when shaken, rendering the remaining product ineffective for future seasons.