It's pouring rain now, but I'll try to get another picture of the stem tomorrow. This is another shot I took earlier today. The leaves start out small and round and grow to about 3" across.

Looks like a type of Ivy, Hedera helix. It will grow very quickly and provide a thick cover. They like moist soil and some shade. You can find it at most garden centers or perennial shops online. Jen

Great..Now that we know what they are, how do you rid of these horrible things..I saw this problem comming when my neighbors decided to let their yard be over run.. They gave up and let them win, until I stepped up to the plate to keep their yard up, and these things keep coming back.... They inched closer and closer to my manicured flower beds, and now I have them.. What works so I can get a head start next year? How do you kill weeds that have root feeders? Maybe Roundup? I hate chemicals..But if this the only way, I will use the stuff, even if it shortens my life..Arg Thanks so much...

More info needed. What tropical climate? Please tell us that you didn't hide it in your luggage to sneak it over the border, lol.