Weeds in groundcover

Asked June 27, 2019, 11:19 AM EDT

Can I use a pre-emergent like Preen on a bed of creeping speedwell ground cover that is fully established to minimize additional weeds?

Cuyahoga County Ohio

1 Response

Pre-emergent herbicides, like Preen, work by forming a barrier in the upper ½ to 1 inch of the mulch or soil where most seeds germinate and kill weeds as they attempt to emerge.

Because these herbicides have no effect on existing weeds, timing the pre-emergent herbicide application properly is critical for success. Because they work prior to weed emergence, applications must occur before weed germination. Any existing weeds should be hand removed. In most cases pre-emergent herbicides should be applied every 2½ to 3 months.

Pre-emergent herbicides can be effective on several annual weeds including crabgrass, goosegrass, spurges, common purslane and mulberry weed. Most perennial weeds such as purple nutsedge and Florida betony are not controlled with pre-emergent herbicides.

Keep in mind that not all weeds spread via seed dispersion. Some weeds spread via there roots. In some cases if even a small portion of a root is left in the soil. it will produce more weeds. Here is a link to the Preen website that lists the weeds that Preen can control by preventing seed germination: https://www.preen.com/products/preen-garden-weed-preventer.

Consult product labels concerning tolerances by desirable plants or contact Preen directly for confirmation that Preen will not harm creeping speedwell.