I recently moved into a house where the front yard was just dirt and a couple of sago palms. No one had lived in the house for a while, and it wasn't being watered. When I planted a couple of things (lavender, etc.) and began watering them, this plant started to pop up and grow all over the front yard. Can anyone identify this? Is it a groundcover or a weed? It is green and looks almost like green apple but has yellow flowers.

Thanks for any help you can give!