Applying Pre-Emergent: Timing Matters
Pre-emergent herbicides are the unsung heroes of weed prevention, forming an invisible barrier in the soil that stops weed seeds from sprouting. Gardening enthusiasts and landscape designers utilize them to maintain their cherished greenery while keeping intrusive plants at bay. Tabar Gifford, a Master Gardener and Partnership Cultivator at American Meadows, explains, "Pre-emergents prevent seeds from germinating, hence the ‘pre’ indicating before, and the ‘emergent’ – as in when seeds start to emerge."
Gifford emphasizes that pre-emergents are non-selective and can inhibit both weed and desirable plant seeds from germinating. Therefore, they should not be applied in areas where seeds will be sown. The ideal time to apply pre-emergents varies depending on the target weed species and regional climate conditions.
For summer annual weeds, like crabgrass, Gifford suggests applying pre-emergents in early spring before the soil temperature reaches 50 to 55 degrees Fahrenheit for five consecutive days. In contrast, winter annual weeds require a fall application to control their germination.
Proper application involves spreading the pre-emergent evenly over the soil and ensuring it remains dry for several days to activate the pre-emergent properties. However, moisture shortly after application can reduce its effectiveness.
Corn Gluten Meal (CGM), a natural byproduct of corn processing, is a popular organic pre-emergent herbicide that can inhibit seed germination by desiccating emerging roots. However, its effectiveness varies and may require multiple applications over a year to two.
Gifford advises using a spreader for granular formulations or a sprayer for liquid pre-emergents, following the manufacturer's instructions to the letter. After application, water the treated area with about 0.5 inches of water to activate the herbicide, unless the product specifies otherwise.
If pre-emergent is applied too early, the herbicide may break down before the weed seeds start to germinate, rendering your efforts futile. On the other hand, if pre-emergent is applied too late and weeds have sprouted, you will need post-emergent herbicides or manual removal efforts.
Combining pre-emergent herbicides with other practices, such as mulching and manual removal, can help maintain a weed-free garden. Regarding safety, always wear gloves, long sleeves, and eye protection while working with pre-emergent herbicides. Keep children and pets away from treated areas until everything is dry and settled.
In some scenarios, using other natural pre-emergents, like products containing citric acid, botanical oils, or vinegar, might be more appropriate. These substances can suppress weed growth, but their effectiveness varies, and they may require multiple applications.
Gifford's tips provide a comprehensive guide for weed management with pre-emergent herbicides. Regardless of your choice of herbicide, the key to success is timely application, proper preparation, and adherence to the manufacturer's instructions.
Pre-emergent herbicides can inhibit the sprouting of desirable plants along with weeds, making it essential to apply them only in areas where seeds will not be sown. For controlling crabgrass, pre-emergents should be applied in early spring before the soil temperature reaches 50 to 55 degrees Fahrenheit. If pre-emergent is applied too early, its effectiveness might be reduced due to breaking down before weed seeds germinate. Corn Gluten Meal, a natural organic pre-emergent, can inhibit seed germination but may require multiple applications for optimal results.
