Preen is a common granular product designed to prevent weed seeds from sprouting in garden beds. This pre-emergent herbicide creates a protective barrier on the soil surface, effectively stopping new weeds before they can establish roots and compete with desirable plants. When dealing with sensitive species like the “Cradle Root,” a delicate or newly established plant, careful and precise application is necessary to protect its health while controlling invasive weeds. This guide provides the instructions needed for effective weed prevention without risking damage to your plants.
Understanding Preen’s Function and Timing
Preen’s primary active ingredient in its standard formulation is often Trifluralin, which acts as a mitotic inhibitor. This chemical does not kill weed seeds directly but rather disrupts cell division in the root and shoot tips of a seed once it begins to germinate. The product must be present in the top layer of soil when the seed starts to sprout, creating a chemical barrier that stops the seedling’s growth before it emerges above ground.
The term “pre-emergent” highlights the time-sensitive nature of the product’s effectiveness. Application must occur before weed seeds start their germination cycle, typically in early spring or before a second flush of summer weeds. If weeds are already visible, Preen will have no effect on them, as their root systems are already established below the shallow barrier zone. Some varieties, like those using corn gluten meal, offer an organic option with a similar pre-emergent effect, but they may require more frequent application to maintain the barrier.
Essential Preparation Before Application
The effectiveness of pre-emergent application relies heavily on thorough preparation of the area. Since the product only targets germinating seeds, all existing visible weeds, including their roots, must be completely removed by hand or hoe. Failing to remove established weeds means they will continue to thrive and produce new seeds.
The soil surface should be lightly cultivated or raked to ensure a smooth, uniform application surface. This process helps the granular product achieve good contact with the soil or mulch layer where the weed seeds reside. Applying Preen requires slightly moist soil for the most immediate activation, so a light watering the day before can be beneficial if the ground is very dry. Always wear personal protective equipment, such as gloves and eye protection, during the preparation and application process.
Step-by-Step Guide to Safe Application
Begin by accurately measuring the area you intend to treat, as applying too much product can harm sensitive plants. The standard application rate for Preen Garden Weed Preventer is approximately one ounce per every ten square feet of garden bed. The granules should be spread as uniformly as possible to ensure the protective barrier is continuous across the entire area.
If using a handheld spreader, set it to a low-to-medium setting to avoid over-concentration in any single spot. If you are applying by hand, use a gentle shaking motion to distribute the granules. After spreading, the product must be activated by moisture to dissolve the active ingredient into the top one to two inches of soil. Immediately water the treated area lightly with a sprinkler or hose, ensuring the moisture soaks in just enough to activate the barrier without washing the granules away.
Specialized Protection for the Cradle Root
Protecting the “Cradle Root” requires establishing an exclusion zone around the plant’s base. Because the active ingredient inhibits root growth, direct contact with the plant’s main root zone can cause injury. The granular product should never be allowed to touch the plant’s stem, crown, or foliage, as this can cause localized damage or discoloration.
Maintain a buffer area of at least three inches away from the base of the plant, extending slightly beyond the drip line where the plant’s feeder roots are concentrated. Preen should not be used on or near any newly transplanted or seeded “Cradle Root” until it is fully established, usually after several months of growth. If the plant is intended for consumption, such as Sea Kale, verify that the specific Preen formulation being used is explicitly approved for edible crops and observe any required pre-harvest intervals listed on the product label.