What Is Pendi and How to Use It for Weed Control

“Pendi” is a common name for pendimethalin, a pre-emergent herbicide used to manage weeds in lawns and gardens. It is classified as a dinitroaniline herbicide and works by preventing weed seeds from developing. This action occurs before the weeds can emerge from the soil, making it a preventative tool. Pendimethalin is absorbed by the roots and shoots of emerging seedlings, where it halts cell division and elongation, which stops the growth process. Its effectiveness relies on creating a chemical barrier on the soil surface that intercepts germinating weeds.

Weeds Controlled by Pendimethalin

Pendimethalin is effective against a wide array of annual grasses and certain broadleaf weeds. Because it only affects germinating seeds, it does not control already established weeds. For grassy weeds, it is commonly used to manage species like:

• Crabgrass
• Foxtail
• Goosegrass
• Barnyardgrass

Beyond grasses, pendimethalin also controls a variety of broadleaf weeds. Homeowners often use it to prevent the emergence of chickweed, knotweed, purslane, and lambsquarter. These weeds can be difficult to manage once they have established a presence, so a pre-emergent application is an effective strategy.

Application Process

Pendimethalin is available in two primary forms: a liquid concentrate and a granular product. The liquid form requires mixing with water in a handheld or backpack sprayer, according to the dilution rates specified on the product label. It is important to ensure the solution is thoroughly mixed to achieve a consistent application. The mixture is then sprayed evenly over the desired treatment area, ensuring complete coverage of the soil surface.

The granular version of pendimethalin is designed for application with a spreader. A broadcast spreader is suitable for covering large, open areas like lawns, casting the granules in a wide, overlapping pattern. For more controlled applications, such as in landscape beds around ornamental plants, a drop spreader can provide more precise placement. The spreader’s setting should be calibrated according to the product’s instructions to deliver the correct amount of granules per square foot.

After applying either the liquid or granular product, it is necessary to water the treated area. Approximately half an inch of water, from either rainfall or irrigation, is needed to move the herbicide from the foliage or granule surface into the top layer of the soil. This watering “activates” the pendimethalin, allowing it to form the chemical barrier in the soil. Without this step, the product may not be effective.

Proper Timing and Location

The timing of a pendimethalin application is an important factor in its success. It must be applied before the target weeds begin to germinate. For many common weeds like crabgrass, this means applying in early spring before the soil temperature consistently reaches 55 degrees Fahrenheit. Using a soil thermometer can help pinpoint the ideal application window. Applying too late will be ineffective against weeds that have already sprouted.

Pendimethalin is intended for use on established turfgrasses and in many ornamental landscape beds where it will not harm mature plants. It can be safely applied over many types of lawn grasses and around a wide variety of shrubs and perennials. This selectivity allows for weed control without damaging existing, desirable vegetation. Always check the product label to confirm it is safe for the specific types of plants in your treatment area.

Certain areas should be avoided when applying this herbicide. It should not be used on newly seeded lawns or on areas where you plan to sow grass seed in the near future, as it will prevent the grass seeds from germinating. Similarly, it is not intended for use in vegetable gardens or on putting greens, unless specified by the product label. Avoiding these areas prevents unintended damage to sensitive plants.

Safety Considerations

When handling and applying pendimethalin, follow the safety instructions detailed on the product label. Personal protective equipment (PPE) should be worn to minimize exposure. This includes waterproof gloves, a long-sleeved shirt, long pants, and closed-toe shoes with socks.

After the application is complete, access to the treated area should be restricted. Keep children and pets off the lawn or out of garden beds until the spray has thoroughly dried or the dust from granules has settled. The product label will provide specific reentry intervals.

Care should be taken to prevent the product from contaminating non-target areas. Avoid applying pendimethalin near wells or in locations where runoff could carry it into storm drains, streams, or other bodies of water. Pendimethalin can be harmful to aquatic organisms, so preventing its movement into waterways is a responsible practice.