I believe that is Ground Ivy....Glechoma hederacea.

Does it look like this?

Here is a link that might be useful: Ground Ivy~Google Images

Looks similar but I don't think it's Ground Ivy. No blossoms, and even when mature the leaves are less than 1/2" and all the same size. (I had lots of mature specimens until recently). Looks the same mature as it does when young.

Thanks for playing though...

appears to be a type of cranesbill or wild geranium. Leaves will shed herbicide. Take a plant to your local nursery to see what it is before you kill it.

That is not "Glechoma hederacea", wrong flowers although the picture does not allow the foliage to be seen. Put a sample in a sealable plastic bag and take it to your local University of California USDA Cooperative Extension Service office for ID.

Here is a link that might be useful: UC CES

Does it have square stems, opposite leaves and a slight minty odor when crushed? Ground Ivy is a member of the often-invasive mint family. Borax sprinkled on damp leaves will kill ground ivy but not wipe out lawn grasses.