Did you check out the Herbarium site Ann (link above)? Gives all the details for identifying plants.
Thank you that info, Lissa. Would be a good link to put on the Weeds pages here on BLF.
Credit where credit is due - thank Jeff. It was his suggestion I just added a link.
Good idea to add the site to the Edible Weeds. Will do that now.
Ann - this is a LINK to many plant identification tools.
I thought it could be catharanthus roseus (Madagascar periwinkle) however I would expect you would have mentioned the pink flowers if it was. I have a plant growing in a jar of water on the windowsill and it seems to be indestructible.
As you have it growing in a buffalo lawn you could try and spray with metsulfuron methyl which is quite a (human) safe selective herbicide that should not damage your turf (I'd suggest a small test area first). This is available in small packs for around $30. You should use a non ionic surfactant with it (eg Nufarm Pulse).
Good research Ann, well done.
I had thought for a bit that it was the ground cover weed growing in my backyard but the flowers are completely different.
How is it recommended that you best get rid of it? Can you pull it out religiously and black bag it? Does it come up again from any roots left behind?