HI, 

The plant in your yard is Ground Ivy (Glechoma hederacea) also known as Creeping Charlie, it is a highly invasive plant in North America.  While native to Europe, it was introduced to the Americas as an ornamental and medicinal plant.  It is very rapidly growing and will overtake a lawn quickly.

In small areas, ground ivy may be managed by pulling and digging. This method is best accomplished after a soaking rain or using a hose to deep water before pulling. Unfortunately, pulling and digging are often ineffective because rarely is the entire plant removed using this method. If the ground ivy is not completely destroyed, surviving portions will continue to grow and spread.

Frequent and persistent removal of ground ivy over the course of several growing seasons as soon as the plant re-emerges may eliminate the weed or keep ground ivy populations low enough to not impact your lawn. Buy the pulling  must be an ongoing task.

For moderate patches you may try smothering the area with cardboard that deprives the plant of light, mulch over the top and plant in the mulch. 

Removing or stripping the Ground Ivy completely and putting down new sod  or seeding offers another solution. This can be costly and labor intensive. If you were to do this, once you seeded or sodded,  you must make sure that proper care is taken  for watering and  maintaining the lawn health.  If you go the seeding route you would want to wait until late summer or early fall to seed.  

 If the infestation is too broad to hand pull  or tackle with other methods, a broadleaf herbicide may be applied to remove the plant.  We recommend this as a last resort. If you choose this option, spot treat weeds with a liquid, selective, postemergent, broadleaf weed killer applied when weeds are actively growing is best. Here is a link to the University of Maryland Extension's recommendations on herbicides.More than one application will be most likely be necessary. Read and follow all of the label directions and recommended precautions when using herbicides. 

I hope this is helpful. Please let us know if you have further questions.

Best regards,

Christine