Hello Karen,

This appears to be one of the types of sow thistle, Sonchus species.

This plant will keep coming back if allowed to flower and produce seeds. Seeds from previous years can continue to sprout many seasons, so you will have to monitor for these for a few years.

The most important thing to get control of weeds is to not let them flower and drop more seeds in your soil. You can keep mowing or cut them off at the soil line with a hoe. You can continue to hand weed out as much as possible. Once killed, mulch the bare soil areas with 4 inches deep of mulch to help suppress weeds from germinating. Applying a pre-emergent (crabgrass preventer) will help prevent so many seed germinating. But do cut any flowers off and discard them in the trash.

You can use weed killer or non-selective herbicide applied to the growing plants. Putting weed killer down a hole will not do any good unfortunately. When the weed killer is applied to a growing plant it is absorbed through the leaves and travels down to the roots and kills the whole plant. Therefore once applied you must leave that weed standing ( you can pinch off any flowers) until it is completely dead in order to give the chemical some time time to travel to the roots, usually 5-10 days.

When treating weeds in the lawn, be sure the weed killer is labeled for use on lawns, or it may kill the grass, too.

Here are some references for you-

https://www.canr.msu.edu/resources/perennial_sowthistle

This article lists the chemical weed killers that are effective. Repeat applications may be necessary.

https://www.nwcb.wa.gov/images/weeds/PERENNIAL-SOWTHISTLE-BROCHURE_Lincoln.pdf

As always, please read and follow all directions on any garden chemical that you use.