How to Mix Trimec Lawn Weed Killer | Rates by Grass Type

Mixing Trimec herbicide requires matching the rate to your grass type. For cool-season lawns, use 4 fl. oz. per gallon per 1,000 sq. ft.

Trimec is one of the most effective broadleaf weed killers for lawns across the US, controlling dandelions, clover, chickweed, and dozens of other common weeds. But the correct mix rate isn’t the same for every lawn. Cool-season grasses like Kentucky bluegrass, tall fescue, and perennial ryegrass handle higher doses without issue, while warm-season grasses like St. Augustine and centipede need roughly half the concentration to avoid turf burn. This guide covers the exact mix rates for every Trimec variant, the step-by-step mixing process, and the mistakes that cost people their lawn.

Trimec Mix Rates by Product and Grass Type

Trimec comes in several formulations — Standard, Crabgrass Plus, Classic, Speed, and Ready Spray — and each has its own mix rate. The table below shows the correct dilution for broadcast and spot treatments across different grass types.

For broadcast coverage, a 32 oz. container of Trimec Standard treats 8,000 sq. ft. on northern lawns or 16,000 sq. ft. on southern lawns where the lower rate is used. If you are comparing products before buying, our roundup of the best lawn killers covers top-rated options for every grass type and treatment need.

How to Mix Trimec Step by Step

The mixing process is the same across all Trimec concentrate formulations. Follow this sequence for a consistent, effective solution.

1. Measure the area. Multiply the length by the width of the treatment area in feet to get square footage. Divide by 43,560 for acres. A 1,000 sq. ft. area is roughly 20 by 50 feet.

2. Half-fill the sprayer tank. Add half the required water first. For hose-end sprayers, pour the product into the jar before adding water — never the reverse order, which can cause improper dilution.

3. Add the measured product. Pour the correct amount of Trimec concentrate into the partial water. Use the table above for the right amount based on your grass type and the specific Trimec variant you have.

4. Fill and agitate. Add the remaining water, close the sprayer, and shake vigorously until the solution looks uniform. The product settles quickly, so shake periodically during application too.

5. Apply evenly. Spray until weed leaves are wet on top and bottom, but stop before runoff. You will see the weeds glisten when properly covered. Do not water the lawn within 24 hours of treatment. Gordon’s official mixing instructions confirm this protocol for all Trimec concentrate products.

Common Mixing Mistakes to Avoid

Using cool-season rates on warm-season grass. This is the most common error and the one most likely to cause visible damage. St. Augustine and centipede lawns burn easily at full strength — always halve the dose when treating these sensitive turfgrasses.

Exceeding the seasonal limit. Trimec Crabgrass Plus allows a maximum of two applications per year with at least 21 days between them. The seasonal cap is 12.8 fl. oz. per 1,000 sq. ft. for that formulation.

Skipping the agitation step. Trimec concentrate settles in water quickly. A vigorous shake before spraying and a brief shake halfway through the job keeps the concentration uniform across the whole treated area.

Applying before rain or watering too soon. Treat only when no rain is forecast for at least 24 hours. Runoff wastes product and can harm adjacent plants or turf. After treatment, wait a full day before running the sprinklers.

Not reading the label for your specific variant. Each Trimec product has different rates and restrictions. The Classic formulation uses much lower per-gallon rates than the Standard or Speed versions, while Crabgrass Plus has strict seasonal limits. Check your bottle’s label before mixing.

FAQs

Can I mix Trimec with other herbicides or fertilizers?

Trimec labels generally advise against tank-mixing with other products unless the label explicitly permits it. Combining herbicides can cause turf damage or reduce the effectiveness of both products. Check your specific product label before mixing anything into the tank.

How long does mixed Trimec stay usable in the sprayer?

Mixed Trimec solution should be applied within 24 hours for best results. The active ingredients remain stable in water for roughly a day, but the solution can settle or degrade if stored longer. Shake thoroughly before reusing if it has sat for a few hours.

What should I do if I accidentally apply too much Trimec?

Over-application can cause turf burn — yellowing or browning of grass blades — especially on warm-season lawns. If you applied too much, water the area lightly the following day to dilute the concentration in the soil, but wait the full 24-hour post-treatment window before doing so.