To control weeds that are sprouting from seed consider using a granular preemergence herbicide that has the active ingredient trifluralin in the early spring. Preen is one brand and there are other brands that contain trifluralin, too. Read the label for the “active  ingredients”, usually found  in small print on the front or back label.

Applying the preemergence herbicide on top of the mulch as directed on the label will help prevent new seed germination.

If you start seeing winter annual weeds a second application time around early-mid August may be recommended. Examples of winter annual weeds can be seen in this article: https://www.canr.msu.edu/news/spring-blooming-lawn-and-garden-weeds

Trifluralin will not control existing weeds or perennials that continue to grow from their roots.

If you can, update this question with a couple clear pictures of the weed you have. We may be able to identify it and give you the correct control options for it. Try pulling a couple with their roots and lay them out to take a picture so we can see the leaves, roots , and any seed pods or flowers.

To attach pictures:

Follow the link in your email into your Ask Ext. Question.

Scroll down to the empty “reply box” and then click the blue “drop files here or choose them”

Follow the prompts to attach pictures from your photos file or app.

Pictures in standard format of jpeg work. Each photo must be 8 megabytes or less in size.

As always please, read nd follow all directions on the label of any product you use.